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I am struggling with a datetime problem where I am given a set of inputs and I need to find the EndDate by using those inputs. I am trying my best to solve this, but since I am running out of time, I landed up here. So someone who already might have faced this problem or someone with a solution could let me know one.
Problem Explanation:
The Concept is a Weekly schedule of a live class streaming application. The teacher has scheduled a weekly class from a specific start date.
Let's say, the start date is from 18th April, 2021 and the teacher selects 3 days per week(Monday, Tuesday & Wednesday) each with different class duration(By duration I mean that, We have the class start time of that day and the length of the class in hours and minutes).
Start Date: 18th April, 2021
Total days per week: 3
Days: Monday, Tuesday, Wednesday
Total duration per day: 3 hrs and 30 minutes
Total duration per week: 10 hours 30 minutes (Aggregated = Mon + Tue + Wed)
Max duration that the user cannot exceed: 50 hrs
Ok! Now we shall repeatedly add the TDPD(3 hrs and 30 minutes) to the start date until we reach 50 hrs and find which date it has landed upon(the end date).
What I have tried so far?
int totalWeeks = 0;
int totalHoursPerWeek = 3;
int totalHoursAdded = 0;
int maxHours = 50;
for(int i = totalHoursPerWeek; i <= maxHours; i += totalHoursPerWeek)
{
totalHoursAdded += i;
totalWeeks++;
}
Once the loop ends, I have the total week value.
DateTime endDate;
if(totalHoursAdded == maxHours)
{
//My problem is solved, as there is no remaining time pending
endDate = currentDate.AddDays(totalWeeks * 7);
}
else
{
// I have some pending hours
int pendingHours = maxHours - totalHoursAdded;
//How do I proceed with this pendingHours? how to add this to the
//specific days per week and find the end date? I am stuck here...
}
I am confident this can be done with some carefully thought-out math with dates, however below may be termed the lazy way out. This approach only needs the starting date, a list of days of the week that the class meets, i.e., Monday, Tuesday etc.…, the duration of the class in hours and minutes, and finally the max total hours and minutes that are required.
From my understanding, given the above info, we want to know, given that start date and the days of the week the class meets…
on what Date will the LAST class be that fulfills the max total hours.
To simplify this, one thing that will come in handy is knowing...
“how many classes are needed to fulfill the MAX requirement”.
In other words, if we know how many classes are needed to fulfill the max requirement, then this should make things easier.
Computing the total number of classes needed to fulfil the max requirement, can be found by dividing the max requirement by the class duration. If the division produces a remainder, then this would mean that one (1) additional class would be needed to fulfil the max requirement.
Therefore, if we have both the class duration and max duration variables as Timespan objects, then, we could divide the TimeSpan objects via their respective Tick properties and return how many classes are needed to fulfil the max requirement. This method may look something like…
private int GetTotalNumberOfClassesNeeded(TimeSpan classDuration, TimeSpan totalDuration) {
double td = totalDuration.Ticks / (double)classDuration.Ticks;
int totalClasses = (int)Math.Truncate(td); // <- get the whole portion
if (Math.Floor(td) != td) {
totalClasses++; // <- there is a fractional part - 1 more class needed
}
return totalClasses;
}
Next, we need to compare the DayOfWeek for a date with the DayOfWeek for the class. Therefore, is what we can do is create a List<DayOfWeek> … a list of DayOfWeek objects that the class is in session. We will use this list to check and see if a particular date’s day of week is IN that list. Therefore, in this example, the days of the week the class meets are a simple comma delimited string. Given this string, the code would parse out the days and return the proper list of DayOfWeek objects to compare with. This method may look something like…
private List<DayOfWeek> GetDaysOfWeekForClasses(string daysOfWeek) {
List<DayOfWeek> classesDOW = new List<DayOfWeek>();
string[] splitArray = daysOfWeek.Split(',');
DayOfWeek dow;
for (int i = 0; i < splitArray.Length; i++) {
switch (splitArray[i].Trim()) {
case "Monday":
dow = DayOfWeek.Monday;
break;
case "Tuesday":
dow = DayOfWeek.Tuesday;
break;
case "Wednesday":
dow = DayOfWeek.Wednesday;
break;
case "Thursday":
dow = DayOfWeek.Thursday;
break;
case "Friday":
dow = DayOfWeek.Friday;
break;
case "Saturday":
dow = DayOfWeek.Saturday;
break;
default:
dow = DayOfWeek.Sunday;
break;
}
classesDOW.Add(dow);
}
return classesDOW;
}
That is pretty much all we need. The general idea is this… we start by setting an int variable curClassCount to zero (0). In addition, we will create a DateTime object tempDate that is initialized with the starting date. Lastly, we will create a list of DateTime objects scheduledClasses which will get filled with the dates of the classes. We will start a while loop with the condition to continue as long as curClassCount is less than the total number of classes needed.
In each iteration of the loop a check is made to see if the tempDate’s DayOfWeek is one of the class’s DayOfWeek. … if it is, then we add that date to the scheduledClasses list and increment curClassCount. Finally increment tempDate by one (1) day, then start the loop over. Eventually, the curClassCount will equal the number of classes needed. This code may look something like…
while (curClassCount < totalNumberOfClassesNeeded) {
if (ClassDaysOfWeek.Contains(tempDate.DayOfWeek)) {
scheduledClasses.Add(tempDate.Date);
curClassCount++;
}
tempDate = tempDate.AddDays(1);
}
Putting all this together by droping a DateTimePicker, four (4) TextBoxes, a Button and a multi-line TextBox onto a new Winforms .Net Form may look something like…
Using the code below should complete the example.
private void Form1_Load(object sender, EventArgs e) {
dateTimePicker1.Value = new DateTime(2021, 4, 18);
TextBoxTotDaysPerWeek.Text = "3";
textBoxClassDays.Text = "Monday, Tuesday, Wednesday";
textBoxClassDuration.Text = "00:03:00:00";
textBoxMaxDuation.Text = "02:02:00:00";
}
private void btnCalculate_Click(object sender, EventArgs e) {
DateTime StartDate = dateTimePicker1.Value;
TimeSpan.TryParse(textBoxClassDuration.Text.Trim(), out TimeSpan ClassDuration);
TimeSpan.TryParse(textBoxMaxDuation.Text.Trim(), out TimeSpan MaxDuration);
int totalNumberOfClassesNeeded = GetTotalNumberOfClassesNeeded(ClassDuration, MaxDuration);
List<DayOfWeek> ClassDaysOfWeek = GetDaysOfWeekForClasses(textBoxClassDays.Text.Trim());
List<DateTime> scheduledClasses = new List<DateTime>();
int curClassCount = 0;
DateTime tempDate = StartDate.Date;
while (curClassCount < totalNumberOfClassesNeeded) {
if (ClassDaysOfWeek.Contains(tempDate.DayOfWeek)) {
scheduledClasses.Add(tempDate.Date);
curClassCount++;
}
tempDate = tempDate.AddDays(1);
}
txtBoxResults.Text = "";
txtBoxResults.Text = "Start Date: " + StartDate.ToShortDateString() +Environment.NewLine;
for (int i = 0; i < scheduledClasses.Count; i++) {
txtBoxResults.Text += "Class # " + (i + 1) + " of " + totalNumberOfClassesNeeded +
" Date: " + scheduledClasses[i].ToShortDateString() + Environment.NewLine;
}
}
A note, on the max duration… since the TimeSpan only allows hours < 23, we need to break 50 hours into 2 days and 2 hours. I hope this makes sense.
These are two options (using For and using While loop), should solve the problem:
using System;
namespace SO.DtProblem
{
class Program
{
static void Main(string[] args)
{
ClaculationOption1(); //Using For loop
ClaculationOption2(); //Using While loop
}
private static void ClaculationOption1()
{
var totalWeeks = 0;
var totalHoursPerWeek = 3;
var durationPerDay = 3;
var maxHours = 50;
var courseStartDate = new DateTime(2021, 4, 12); //Which is a Monday day
totalWeeks = maxHours / totalHoursPerWeek;
var expectedEndDate = courseStartDate.AddDays(totalWeeks * 7);
var pendingHours = maxHours % totalHoursPerWeek;
for (var day = 1; day <= 6; day++)
{
if (pendingHours > 0)
{
expectedEndDate = expectedEndDate.AddDays(1);
if ((expectedEndDate.AddDays(1).DayOfWeek == DayOfWeek.Monday)
|| (expectedEndDate.AddDays(1).DayOfWeek == DayOfWeek.Tuesday)
|| (expectedEndDate.AddDays(1).DayOfWeek == DayOfWeek.Wednesday))
{
if (pendingHours - durationPerDay >= 0)
{
pendingHours = pendingHours - durationPerDay;
}
else
{
pendingHours = 0;
break;
}
}
}
}
Console.Clear();
Console.WriteLine("Option 1 Results");
Console.WriteLine($"Course Start Date : {courseStartDate}");
Console.WriteLine($"Course Start Date Day Name: {courseStartDate.DayOfWeek}");
Console.WriteLine($"Expected End Date : {expectedEndDate}");
Console.WriteLine($"Expected End Date Day Name: {expectedEndDate.DayOfWeek}");
Console.WriteLine("===========================================================");
}
private static void ClaculationOption2()
{
var totalWeeks = 0;
var totalHoursPerWeek = 3;
var durationPerDay = 3;
var maxHours = 50;
var courseStartDate = new DateTime(2021, 4, 12); //Which is a Monday day
totalWeeks = maxHours / totalHoursPerWeek;
var expectedEndDate = courseStartDate.AddDays(totalWeeks * 7);
var pendingHours = maxHours % totalHoursPerWeek;
while (pendingHours > 0)
{
expectedEndDate = expectedEndDate.AddDays(1);
if ((expectedEndDate.AddDays(1).DayOfWeek == DayOfWeek.Monday)
|| (expectedEndDate.AddDays(1).DayOfWeek == DayOfWeek.Tuesday)
|| (expectedEndDate.AddDays(1).DayOfWeek == DayOfWeek.Wednesday))
{
if (pendingHours - durationPerDay >= 0)
{
pendingHours = pendingHours - durationPerDay;
}
else
{
pendingHours = 0;
break;
}
}
}
Console.WriteLine("Option 2 Results");
Console.WriteLine($"Course Start Date : {courseStartDate}");
Console.WriteLine($"Course Start Date Day Name: {courseStartDate.DayOfWeek}");
Console.WriteLine($"Expected End Date : {expectedEndDate}");
Console.WriteLine($"Expected End Date Day Name: {expectedEndDate.DayOfWeek}");
Console.ReadKey();
}
}
}
Finally I got my own solution working on the idea based on #John's answer. This answer is specially for the variable hours and minutes.
private static void CalculateClassDates()
{
DateTime courseStartDateTime = DateTime.Today;
int courseDurationInHours = 60;
int courseDurationInMinutes = 0;
TimeSpan courseMaxDuration = new TimeSpan(courseDurationInHours, courseDurationInMinutes, 0);
List<CourseScheduleDates> courseScheduleDates = new List<CourseScheduleDates>();
List<DaysOfWeek> daysOfWeeks = new List<DaysOfWeek>()
{
new DaysOfWeek(){ DayOfWeek = DayOfWeek.Monday, StartTime = DateTime.Today.AddHours(10).TimeOfDay , TotalHours = 1, TotalMinutes = 15},
new DaysOfWeek(){ DayOfWeek = DayOfWeek.Tuesday, StartTime = DateTime.Today.AddHours(10).TimeOfDay , TotalHours = 1, TotalMinutes = 15},
new DaysOfWeek(){ DayOfWeek = DayOfWeek.Wednesday, StartTime = DateTime.Today.AddHours(10).TimeOfDay , TotalHours = 1, TotalMinutes = 30}
};
int daysToAdd = 0;
TimeSpan singleDuration = new TimeSpan(daysOfWeeks[0].TotalHours, daysOfWeeks[0].TotalMinutes, 0);
TimeSpan additionallyAddedTime = TimeSpan.Zero;
List<DayOfWeek> days = daysOfWeeks.Select(x => x.DayOfWeek).ToList();
while (singleDuration.Ticks <= courseMaxDuration.Ticks)
{
if (days.Contains(courseStartDateTime.AddDays(daysToAdd).DayOfWeek))
{
var dayOfWeek = daysOfWeeks.Where(x => x.DayOfWeek == courseStartDateTime.AddDays(daysToAdd).DayOfWeek).First();
courseScheduleDates.Add(new CourseScheduleDates()
{
ScheduleDate = courseStartDateTime.AddDays(daysToAdd),
StartTime = dayOfWeek.StartTime,
TotalHours = dayOfWeek.TotalHours,
TotalMinutes = dayOfWeek.TotalMinutes
});
additionallyAddedTime = new TimeSpan(dayOfWeek.TotalHours, dayOfWeek.TotalMinutes, 0);
singleDuration = singleDuration.Add(additionallyAddedTime);
}
daysToAdd++;
}
singleDuration = singleDuration.Subtract(additionallyAddedTime);
if (singleDuration.Ticks != courseMaxDuration.Ticks)
{
var timeSpanToAdd = new TimeSpan(courseMaxDuration.Ticks - singleDuration.Ticks);
bool shouldContinue = true;
while (shouldContinue)
{
var currentDate = courseStartDateTime.AddDays(daysToAdd);
if (days.Contains(currentDate.DayOfWeek))
{
var dayOfWeek = daysOfWeeks.Where(x => x.DayOfWeek == courseStartDateTime.DayOfWeek).First();
courseScheduleDates.Add(new CourseScheduleDates()
{
ScheduleDate = courseStartDateTime.AddDays(daysToAdd),
StartTime = dayOfWeek.StartTime,
TotalHours = timeSpanToAdd.Hours,
TotalMinutes = timeSpanToAdd.Minutes
});
shouldContinue = false;
}
}
}
Console.WriteLine("Course Start Date " + courseStartDateTime.ToString("dd MMM, yyyy"));
int classCount = 1;
foreach (var item in courseScheduleDates)
{
DateTime dateTime = new DateTime(item.StartTime.Ticks);
Console.WriteLine("Class " + classCount + " will commence on " + item.ScheduleDate.ToString("dd MMM, yyyy") +
" " + dateTime.ToString("hh:mm tt") + " and will last for " + item.TotalHours + " hrs " + item.TotalMinutes + " mins");
classCount++;
}
Console.ReadLine();
}
And the Models
public class DaysOfWeek
{
public DayOfWeek DayOfWeek { get; set; }
public TimeSpan StartTime { get; set; }
public int TotalHours { get; set; }
public int TotalMinutes { get; set; }
}
public class CourseScheduleDates
{
public DateTime ScheduleDate { get; set; }
public TimeSpan StartTime { get; set; }
public int TotalHours { get; set; }
public int TotalMinutes { get; set; }
}
How to calculate the difference in months between two dates in C#?
Is there is equivalent of VB's DateDiff() method in C#. I need to find difference in months between two dates that are years apart. The documentation says that I can use TimeSpan like:
TimeSpan ts = date1 - date2;
but this gives me data in Days. I don't want to divide this number by 30 because not every month is 30 days and since the two operand values are quite apart from each other, I am afraid dividing by 30 might give me a wrong value.
Any suggestions?
Assuming the day of the month is irrelevant (i.e. the diff between 2011.1.1 and 2010.12.31 is 1), with date1 > date2 giving a positive value and date2 > date1 a negative value
((date1.Year - date2.Year) * 12) + date1.Month - date2.Month
Or, assuming you want an approximate number of 'average months' between the two dates, the following should work for all but very huge date differences.
date1.Subtract(date2).Days / (365.25 / 12)
Note, if you were to use the latter solution then your unit tests should state the widest date range which your application is designed to work with and validate the results of the calculation accordingly.
Update (with thanks to Gary)
If using the 'average months' method, a slightly more accurate number to use for the 'average number of days per year' is 365.2425.
Here is a comprehensive solution to return a DateTimeSpan, similar to a TimeSpan, except that it includes all the date components in addition to the time components.
Usage:
void Main()
{
DateTime compareTo = DateTime.Parse("8/13/2010 8:33:21 AM");
DateTime now = DateTime.Parse("2/9/2012 10:10:11 AM");
var dateSpan = DateTimeSpan.CompareDates(compareTo, now);
Console.WriteLine("Years: " + dateSpan.Years);
Console.WriteLine("Months: " + dateSpan.Months);
Console.WriteLine("Days: " + dateSpan.Days);
Console.WriteLine("Hours: " + dateSpan.Hours);
Console.WriteLine("Minutes: " + dateSpan.Minutes);
Console.WriteLine("Seconds: " + dateSpan.Seconds);
Console.WriteLine("Milliseconds: " + dateSpan.Milliseconds);
}
Outputs:
Years: 1
Months: 5
Days: 27
Hours: 1
Minutes: 36
Seconds: 50
Milliseconds: 0
For convenience, I've lumped the logic into the DateTimeSpan struct, but you may move the method CompareDates wherever you see fit. Also note, it doesn't matter which date comes before the other.
public struct DateTimeSpan
{
public int Years { get; }
public int Months { get; }
public int Days { get; }
public int Hours { get; }
public int Minutes { get; }
public int Seconds { get; }
public int Milliseconds { get; }
public DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)
{
Years = years;
Months = months;
Days = days;
Hours = hours;
Minutes = minutes;
Seconds = seconds;
Milliseconds = milliseconds;
}
enum Phase { Years, Months, Days, Done }
public static DateTimeSpan CompareDates(DateTime date1, DateTime date2)
{
if (date2 < date1)
{
var sub = date1;
date1 = date2;
date2 = sub;
}
DateTime current = date1;
int years = 0;
int months = 0;
int days = 0;
Phase phase = Phase.Years;
DateTimeSpan span = new DateTimeSpan();
int officialDay = current.Day;
while (phase != Phase.Done)
{
switch (phase)
{
case Phase.Years:
if (current.AddYears(years + 1) > date2)
{
phase = Phase.Months;
current = current.AddYears(years);
}
else
{
years++;
}
break;
case Phase.Months:
if (current.AddMonths(months + 1) > date2)
{
phase = Phase.Days;
current = current.AddMonths(months);
if (current.Day < officialDay && officialDay <= DateTime.DaysInMonth(current.Year, current.Month))
current = current.AddDays(officialDay - current.Day);
}
else
{
months++;
}
break;
case Phase.Days:
if (current.AddDays(days + 1) > date2)
{
current = current.AddDays(days);
var timespan = date2 - current;
span = new DateTimeSpan(years, months, days, timespan.Hours, timespan.Minutes, timespan.Seconds, timespan.Milliseconds);
phase = Phase.Done;
}
else
{
days++;
}
break;
}
}
return span;
}
}
You could do
if ( date1.AddMonths(x) > date2 )
If you want the exact number of full months, always positive (2000-01-15, 2000-02-14 returns 0), considering a full month is when you reach the same day the next month (something like the age calculation)
public static int GetMonthsBetween(DateTime from, DateTime to)
{
if (from > to) return GetMonthsBetween(to, from);
var monthDiff = Math.Abs((to.Year * 12 + (to.Month - 1)) - (from.Year * 12 + (from.Month - 1)));
if (from.AddMonths(monthDiff) > to || to.Day < from.Day)
{
return monthDiff - 1;
}
else
{
return monthDiff;
}
}
Edit reason: the old code was not correct in some cases like :
new { From = new DateTime(1900, 8, 31), To = new DateTime(1901, 8, 30), Result = 11 },
Test cases I used to test the function:
var tests = new[]
{
new { From = new DateTime(1900, 1, 1), To = new DateTime(1900, 1, 1), Result = 0 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1900, 1, 2), Result = 0 },
new { From = new DateTime(1900, 1, 2), To = new DateTime(1900, 1, 1), Result = 0 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1900, 2, 1), Result = 1 },
new { From = new DateTime(1900, 2, 1), To = new DateTime(1900, 1, 1), Result = 1 },
new { From = new DateTime(1900, 1, 31), To = new DateTime(1900, 2, 1), Result = 0 },
new { From = new DateTime(1900, 8, 31), To = new DateTime(1900, 9, 30), Result = 0 },
new { From = new DateTime(1900, 8, 31), To = new DateTime(1900, 10, 1), Result = 1 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1901, 1, 1), Result = 12 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1911, 1, 1), Result = 132 },
new { From = new DateTime(1900, 8, 31), To = new DateTime(1901, 8, 30), Result = 11 },
};
I checked the usage of this method in VB.NET via MSDN and it seems that it has a lot of usages. There is no such a built-in method in C#. (Even it's not a good idea) you can call VB's in C#.
Add Microsoft.VisualBasic.dll to
your project as a reference
use
Microsoft.VisualBasic.DateAndTime.DateDiff
in your code
Use Noda Time:
LocalDate start = new LocalDate(2013, 1, 5);
LocalDate end = new LocalDate(2014, 6, 1);
Period period = Period.Between(start, end, PeriodUnits.Months);
Console.WriteLine(period.Months); // 16
(example source)
To get difference in months (both start and end inclusive), irrespective of dates:
DateTime start = new DateTime(2013, 1, 1);
DateTime end = new DateTime(2014, 2, 1);
var diffMonths = (end.Month + end.Year * 12) - (start.Month + start.Year * 12);
I just needed something simple to cater for e.g. employment dates where only the month/year is entered, so wanted distinct years and months worked in. This is what I use, here for usefullness only
public static YearsMonths YearMonthDiff(DateTime startDate, DateTime endDate) {
int monthDiff = ((endDate.Year * 12) + endDate.Month) - ((startDate.Year * 12) + startDate.Month) + 1;
int years = (int)Math.Floor((decimal) (monthDiff / 12));
int months = monthDiff % 12;
return new YearsMonths {
TotalMonths = monthDiff,
Years = years,
Months = months
};
}
.NET Fiddle
You can use Noda Time https://nodatime.org/
LocalDate start = new LocalDate(2010, 1, 5);
LocalDate end = new LocalDate(2012, 6, 1);
Period period = Period.Between(start, end, PeriodUnits.Months);
Console.WriteLine(period.Months);
You can use the DateDiff class of the Time Period Library for .NET:
// ----------------------------------------------------------------------
public void DateDiffSample()
{
DateTime date1 = new DateTime( 2009, 11, 8, 7, 13, 59 );
DateTime date2 = new DateTime( 2011, 3, 20, 19, 55, 28 );
DateDiff dateDiff = new DateDiff( date1, date2 );
// differences
Console.WriteLine( "DateDiff.Months: {0}", dateDiff.Months );
// > DateDiff.Months: 16
// elapsed
Console.WriteLine( "DateDiff.ElapsedMonths: {0}", dateDiff.ElapsedMonths );
// > DateDiff.ElapsedMonths: 4
// description
Console.WriteLine( "DateDiff.GetDescription(6): {0}", dateDiff.GetDescription( 6 ) );
// > DateDiff.GetDescription(6): 1 Year 4 Months 12 Days 12 Hours 41 Mins 29 Secs
} // DateDiffSample
Here is my contribution to get difference in Months that I've found to be accurate:
namespace System
{
public static class DateTimeExtensions
{
public static Int32 DiffMonths( this DateTime start, DateTime end )
{
Int32 months = 0;
DateTime tmp = start;
while ( tmp < end )
{
months++;
tmp = tmp.AddMonths( 1 );
}
return months;
}
}
}
Usage:
Int32 months = DateTime.Now.DiffMonths( DateTime.Now.AddYears( 5 ) );
You can create another method called DiffYears and apply exactly the same logic as above and AddYears instead of AddMonths in the while loop.
This worked for what I needed it for. The day of month didn't matter in my case because it always happens to be the last day of the month.
public static int MonthDiff(DateTime d1, DateTime d2){
int retVal = 0;
if (d1.Month<d2.Month)
{
retVal = (d1.Month + 12) - d2.Month;
retVal += ((d1.Year - 1) - d2.Year)*12;
}
else
{
retVal = d1.Month - d2.Month;
retVal += (d1.Year - d2.Year)*12;
}
//// Calculate the number of years represented and multiply by 12
//// Substract the month number from the total
//// Substract the difference of the second month and 12 from the total
//retVal = (d1.Year - d2.Year) * 12;
//retVal = retVal - d1.Month;
//retVal = retVal - (12 - d2.Month);
return retVal;
}
There's 3 cases: same year, previous year and other years.
If the day of the month does not matter...
public int GetTotalNumberOfMonths(DateTime start, DateTime end)
{
// work with dates in the right order
if (start > end)
{
var swapper = start;
start = end;
end = swapper;
}
switch (end.Year - start.Year)
{
case 0: // Same year
return end.Month - start.Month;
case 1: // last year
return (12 - start.Month) + end.Month;
default:
return 12 * (3 - (end.Year - start.Year)) + (12 - start.Month) + end.Month;
}
}
The most precise way is this that return difference in months by fraction :
private double ReturnDiffereceBetweenTwoDatesInMonths(DateTime startDateTime, DateTime endDateTime)
{
double result = 0;
double days = 0;
DateTime currentDateTime = startDateTime;
while (endDateTime > currentDateTime.AddMonths(1))
{
result ++;
currentDateTime = currentDateTime.AddMonths(1);
}
if (endDateTime > currentDateTime)
{
days = endDateTime.Subtract(currentDateTime).TotalDays;
}
return result + days/endDateTime.GetMonthDays;
}
My understanding of the total months difference between 2 dates has an integral and a fractional part (the date matters).
The integral part is the full months difference.
The fractional part, for me, is the difference of the % of the day (to the full days of month) between the starting and ending months.
public static class DateTimeExtensions
{
public static double TotalMonthsDifference(this DateTime from, DateTime to)
{
//Compute full months difference between dates
var fullMonthsDiff = (to.Year - from.Year)*12 + to.Month - from.Month;
//Compute difference between the % of day to full days of each month
var fractionMonthsDiff = ((double)(to.Day-1) / (DateTime.DaysInMonth(to.Year, to.Month)-1)) -
((double)(from.Day-1)/ (DateTime.DaysInMonth(from.Year, from.Month)-1));
return fullMonthsDiff + fractionMonthsDiff;
}
}
With this extension, those are the results:
2/29/2000 TotalMonthsDifference 2/28/2001 => 12
2/28/2000 TotalMonthsDifference 2/28/2001 => 12.035714285714286
01/01/2000 TotalMonthsDifference 01/16/2000 => 0.5
01/31/2000 TotalMonthsDifference 01/01/2000 => -1.0
01/31/2000 TotalMonthsDifference 02/29/2000 => 1.0
01/31/2000 TotalMonthsDifference 02/28/2000 => 0.9642857142857143
01/31/2001 TotalMonthsDifference 02/28/2001 => 1.0
Here is a simple solution that works at least for me. It's probably not the fastest though because it uses the cool DateTime's AddMonth feature in a loop:
public static int GetMonthsDiff(DateTime start, DateTime end)
{
if (start > end)
return GetMonthsDiff(end, start);
int months = 0;
do
{
start = start.AddMonths(1);
if (start > end)
return months;
months++;
}
while (true);
}
This simple static function calculates the fraction of months between two Datetimes, e.g.
1.1. to 31.1. = 1.0
1.4. to 15.4. = 0.5
16.4. to 30.4. = 0.5
1.3. to 1.4. = 1 + 1/30
The function assumes that the first date is smaller than the second date. To deal with negative time intervals one can modify the function easily by introducing a sign and a variable swap at the beginning.
public static double GetDeltaMonths(DateTime t0, DateTime t1)
{
DateTime t = t0;
double months = 0;
while(t<=t1)
{
int daysInMonth = DateTime.DaysInMonth(t.Year, t.Month);
DateTime endOfMonth = new DateTime(t.Year, t.Month, daysInMonth);
int cutDay = endOfMonth <= t1 ? daysInMonth : t1.Day;
months += (cutDay - t.Day + 1) / (double) daysInMonth;
t = new DateTime(t.Year, t.Month, 1).AddMonths(1);
}
return Math.Round(months,2);
}
one line solution
For first, check if both dates are in the current year, if not get months of whole years and then add months from the start and end year.
DateTime dateFrom = new DateTime(2019, 2, 1);
DateTime dateTo = new DateTime(2021, 5, 25);
With the first month
var monthCount = dateFrom.Year != dateTo.Year ? ((dateTo.Year - dateFrom.Year - 1) * 12) + (13 - dateFrom.Month + dateTo.Month) : dateTo.Month - dateFrom.Month + 1;
result = 28
Without first month
monthCount = dateFrom.Year != dateTo.Year ? ((dateTo.Year - dateFrom.Year - 1) * 12) + (12 - dateFrom.Month + dateTo.Month) : dateTo.Month - dateFrom.Month;
result = 27
Public Class ClassDateOperation
Private prop_DifferenceInDay As Integer
Private prop_DifferenceInMonth As Integer
Private prop_DifferenceInYear As Integer
Public Function DayMonthYearFromTwoDate(ByVal DateStart As Date, ByVal DateEnd As Date) As ClassDateOperation
Dim differenceInDay As Integer
Dim differenceInMonth As Integer
Dim differenceInYear As Integer
Dim myDate As Date
DateEnd = DateEnd.AddDays(1)
differenceInYear = DateEnd.Year - DateStart.Year
If DateStart.Month <= DateEnd.Month Then
differenceInMonth = DateEnd.Month - DateStart.Month
Else
differenceInYear -= 1
differenceInMonth = (12 - DateStart.Month) + DateEnd.Month
End If
If DateStart.Day <= DateEnd.Day Then
differenceInDay = DateEnd.Day - DateStart.Day
Else
myDate = CDate("01/" & DateStart.AddMonths(1).Month & "/" & DateStart.Year).AddDays(-1)
If differenceInMonth <> 0 Then
differenceInMonth -= 1
Else
differenceInMonth = 11
differenceInYear -= 1
End If
differenceInDay = myDate.Day - DateStart.Day + DateEnd.Day
End If
prop_DifferenceInDay = differenceInDay
prop_DifferenceInMonth = differenceInMonth
prop_DifferenceInYear = differenceInYear
Return Me
End Function
Public ReadOnly Property DifferenceInDay() As Integer
Get
Return prop_DifferenceInDay
End Get
End Property
Public ReadOnly Property DifferenceInMonth As Integer
Get
Return prop_DifferenceInMonth
End Get
End Property
Public ReadOnly Property DifferenceInYear As Integer
Get
Return prop_DifferenceInYear
End Get
End Property
End Class
This is from my own library, will return the difference of months between two dates.
public static int MonthDiff(DateTime d1, DateTime d2)
{
int retVal = 0;
// Calculate the number of years represented and multiply by 12
// Substract the month number from the total
// Substract the difference of the second month and 12 from the total
retVal = (d1.Year - d2.Year) * 12;
retVal = retVal - d1.Month;
retVal = retVal - (12 - d2.Month);
return retVal;
}
You can have a function something like this.
For Example, from 2012/12/27 to 2012/12/29 becomes 3 days. Likewise, from 2012/12/15 to 2013/01/15 becomes 2 months, because up to 2013/01/14 it's 1 month. from 15th it's 2nd month started.
You can remove the "=" in the second if condition, if you do not want to include both days in the calculation. i.e, from 2012/12/15 to 2013/01/15 is 1 month.
public int GetMonths(DateTime startDate, DateTime endDate)
{
if (startDate > endDate)
{
throw new Exception("Start Date is greater than the End Date");
}
int months = ((endDate.Year * 12) + endDate.Month) - ((startDate.Year * 12) + startDate.Month);
if (endDate.Day >= startDate.Day)
{
months++;
}
return months;
}
you can use the following extension:
Code
public static class Ext
{
#region Public Methods
public static int GetAge(this DateTime #this)
{
var today = DateTime.Today;
return ((((today.Year - #this.Year) * 100) + (today.Month - #this.Month)) * 100 + today.Day - #this.Day) / 10000;
}
public static int DiffMonths(this DateTime #from, DateTime #to)
{
return (((((#to.Year - #from.Year) * 12) + (#to.Month - #from.Month)) * 100 + #to.Day - #from.Day) / 100);
}
public static int DiffYears(this DateTime #from, DateTime #to)
{
return ((((#to.Year - #from.Year) * 100) + (#to.Month - #from.Month)) * 100 + #to.Day - #from.Day) / 10000;
}
#endregion Public Methods
}
Implementation !
int Age;
int years;
int Months;
//Replace your own date
var d1 = new DateTime(2000, 10, 22);
var d2 = new DateTime(2003, 10, 20);
//Age
Age = d1.GetAge();
Age = d2.GetAge();
//positive
years = d1.DiffYears(d2);
Months = d1.DiffMonths(d2);
//negative
years = d2.DiffYears(d1);
Months = d2.DiffMonths(d1);
//Or
Months = Ext.DiffMonths(d1, d2);
years = Ext.DiffYears(d1, d2);
Here's a much more concise solution using VB.Net DateDiff for Year, Month, Day only. You can load the DateDiff library in C# as well.
date1 must be <= date2
VB.NET
Dim date1 = Now.AddDays(-2000)
Dim date2 = Now
Dim diffYears = DateDiff(DateInterval.Year, date1, date2) - If(date1.DayOfYear > date2.DayOfYear, 1, 0)
Dim diffMonths = DateDiff(DateInterval.Month, date1, date2) - diffYears * 12 - If(date1.Day > date2.Day, 1, 0)
Dim diffDays = If(date2.Day >= date1.Day, date2.Day - date1.Day, date2.Day + (Date.DaysInMonth(date1.Year, date1.Month) - date1.Day))
C#
DateTime date1 = Now.AddDays(-2000);
DateTime date2 = Now;
int diffYears = DateDiff(DateInterval.Year, date1, date2) - date1.DayOfYear > date2.DayOfYear ? 1 : 0;
int diffMonths = DateDiff(DateInterval.Month, date1, date2) - diffYears * 12 - date1.Day > date2.Day ? 1 : 0;
int diffDays = date2.Day >= date1.Day ? date2.Day - date1.Day : date2.Day + (System.DateTime.DaysInMonth(date1.Year, date1.Month) - date1.Day);
This is in response to Kirk Woll's answer. I don't have enough reputation points to reply to a comment yet...
I liked Kirk's solution and was going to shamelessly rip it off and use it in my code, but when I looked through it I realized it's way too complicated. Unnecessary switching and looping, and a public constructor that is pointless to use.
Here's my rewrite:
public class DateTimeSpan {
private DateTime _date1;
private DateTime _date2;
private int _years;
private int _months;
private int _days;
private int _hours;
private int _minutes;
private int _seconds;
private int _milliseconds;
public int Years { get { return _years; } }
public int Months { get { return _months; } }
public int Days { get { return _days; } }
public int Hours { get { return _hours; } }
public int Minutes { get { return _minutes; } }
public int Seconds { get { return _seconds; } }
public int Milliseconds { get { return _milliseconds; } }
public DateTimeSpan(DateTime date1, DateTime date2) {
_date1 = (date1 > date2) ? date1 : date2;
_date2 = (date2 < date1) ? date2 : date1;
_years = _date1.Year - _date2.Year;
_months = (_years * 12) + _date1.Month - _date2.Month;
TimeSpan t = (_date2 - _date1);
_days = t.Days;
_hours = t.Hours;
_minutes = t.Minutes;
_seconds = t.Seconds;
_milliseconds = t.Milliseconds;
}
public static DateTimeSpan CompareDates(DateTime date1, DateTime date2) {
return new DateTimeSpan(date1, date2);
}
}
Usage1, pretty much the same:
void Main()
{
DateTime compareTo = DateTime.Parse("8/13/2010 8:33:21 AM");
DateTime now = DateTime.Parse("2/9/2012 10:10:11 AM");
var dateSpan = new DateTimeSpan(compareTo, now);
Console.WriteLine("Years: " + dateSpan.Years);
Console.WriteLine("Months: " + dateSpan.Months);
Console.WriteLine("Days: " + dateSpan.Days);
Console.WriteLine("Hours: " + dateSpan.Hours);
Console.WriteLine("Minutes: " + dateSpan.Minutes);
Console.WriteLine("Seconds: " + dateSpan.Seconds);
Console.WriteLine("Milliseconds: " + dateSpan.Milliseconds);
}
Usage2, similar:
void Main()
{
DateTime compareTo = DateTime.Parse("8/13/2010 8:33:21 AM");
DateTime now = DateTime.Parse("2/9/2012 10:10:11 AM");
Console.WriteLine("Years: " + DateTimeSpan.CompareDates(compareTo, now).Years);
Console.WriteLine("Months: " + DateTimeSpan.CompareDates(compareTo, now).Months);
Console.WriteLine("Days: " + DateTimeSpan.CompareDates(compareTo, now).Days);
Console.WriteLine("Hours: " + DateTimeSpan.CompareDates(compareTo, now).Hours);
Console.WriteLine("Minutes: " + DateTimeSpan.CompareDates(compareTo, now).Minutes);
Console.WriteLine("Seconds: " + DateTimeSpan.CompareDates(compareTo, now).Seconds);
Console.WriteLine("Milliseconds: " + DateTimeSpan.CompareDates(compareTo, now).Milliseconds);
}
In my case it is required to calculate the complete month from the start date to the day prior to this day in the next month or from start to end of month.
Ex: from 1/1/2018 to 31/1/2018 is a complete month
Ex2: from 5/1/2018 to 4/2/2018 is a complete month
so based on this here is my solution:
public static DateTime GetMonthEnd(DateTime StartDate, int MonthsCount = 1)
{
return StartDate.AddMonths(MonthsCount).AddDays(-1);
}
public static Tuple<int, int> CalcPeriod(DateTime StartDate, DateTime EndDate)
{
int MonthsCount = 0;
Tuple<int, int> Period;
while (true)
{
if (GetMonthEnd(StartDate) > EndDate)
break;
else
{
MonthsCount += 1;
StartDate = StartDate.AddMonths(1);
}
}
int RemainingDays = (EndDate - StartDate).Days + 1;
Period = new Tuple<int, int>(MonthsCount, RemainingDays);
return Period;
}
Usage:
Tuple<int, int> Period = CalcPeriod(FromDate, ToDate);
Note: in my case it was required to calculate the remaining days after the complete months so if it's not your case you could ignore the days result or even you could change the method return from tuple to integer.
public static int PayableMonthsInDuration(DateTime StartDate, DateTime EndDate)
{
int sy = StartDate.Year; int sm = StartDate.Month; int count = 0;
do
{
count++;if ((sy == EndDate.Year) && (sm >= EndDate.Month)) { break; }
sm++;if (sm == 13) { sm = 1; sy++; }
} while ((EndDate.Year >= sy) || (EndDate.Month >= sm));
return (count);
}
This solution is for Rental/subscription calculation, where difference doesn't means to be subtraction, it's meant to be the span in within those two dates.
I wrote a function to accomplish this, because the others ways weren't working for me.
public string getEndDate (DateTime startDate,decimal monthCount)
{
int y = startDate.Year;
int m = startDate.Month;
for (decimal i = monthCount; i > 1; i--)
{
m++;
if (m == 12)
{ y++;
m = 1;
}
}
return string.Format("{0}-{1}-{2}", y.ToString(), m.ToString(), startDate.Day.ToString());
}
There are not a lot of clear answers on this because you are always assuming things.
This solution calculates between two dates the months between assuming you want to save the day of month for comparison, (meaning that the day of the month is considered in the calculation)
Example, if you have a date of 30 Jan 2012, 29 Feb 2012 will not be a month but 01 March 2013 will.
It's been tested pretty thoroughly, probably will clean it up later as we use it, but here:
private static int TotalMonthDifference(DateTime dtThis, DateTime dtOther)
{
int intReturn = 0;
bool sameMonth = false;
if (dtOther.Date < dtThis.Date) //used for an error catch in program, returns -1
intReturn--;
int dayOfMonth = dtThis.Day; //captures the month of day for when it adds a month and doesn't have that many days
int daysinMonth = 0; //used to caputre how many days are in the month
while (dtOther.Date > dtThis.Date) //while Other date is still under the other
{
dtThis = dtThis.AddMonths(1); //as we loop, we just keep adding a month for testing
daysinMonth = DateTime.DaysInMonth(dtThis.Year, dtThis.Month); //grabs the days in the current tested month
if (dtThis.Day != dayOfMonth) //Example 30 Jan 2013 will go to 28 Feb when a month is added, so when it goes to march it will be 28th and not 30th
{
if (daysinMonth < dayOfMonth) // uses day in month max if can't set back to day of month
dtThis.AddDays(daysinMonth - dtThis.Day);
else
dtThis.AddDays(dayOfMonth - dtThis.Day);
}
if (((dtOther.Year == dtThis.Year) && (dtOther.Month == dtThis.Month))) //If the loop puts it in the same month and year
{
if (dtOther.Day >= dayOfMonth) //check to see if it is the same day or later to add one to month
intReturn++;
sameMonth = true; //sets this to cancel out of the normal counting of month
}
if ((!sameMonth)&&(dtOther.Date > dtThis.Date))//so as long as it didn't reach the same month (or if i started in the same month, one month ahead, add a month)
intReturn++;
}
return intReturn; //return month
}
Based on the excellent DateTimeSpan work done above, I've normalized the code a bit; this seems to work pretty well:
public class DateTimeSpan
{
private DateTimeSpan() { }
private DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)
{
Years = years;
Months = months;
Days = days;
Hours = hours;
Minutes = minutes;
Seconds = seconds;
Milliseconds = milliseconds;
}
public int Years { get; private set; } = 0;
public int Months { get; private set; } = 0;
public int Days { get; private set; } = 0;
public int Hours { get; private set; } = 0;
public int Minutes { get; private set; } = 0;
public int Seconds { get; private set; } = 0;
public int Milliseconds { get; private set; } = 0;
public static DateTimeSpan CompareDates(DateTime StartDate, DateTime EndDate)
{
if (StartDate.Equals(EndDate)) return new DateTimeSpan();
DateTimeSpan R = new DateTimeSpan();
bool Later;
if (Later = StartDate > EndDate)
{
DateTime D = StartDate;
StartDate = EndDate;
EndDate = D;
}
// Calculate Date Stuff
for (DateTime D = StartDate.AddYears(1); D < EndDate; D = D.AddYears(1), R.Years++) ;
if (R.Years > 0) StartDate = StartDate.AddYears(R.Years);
for (DateTime D = StartDate.AddMonths(1); D < EndDate; D = D.AddMonths(1), R.Months++) ;
if (R.Months > 0) StartDate = StartDate.AddMonths(R.Months);
for (DateTime D = StartDate.AddDays(1); D < EndDate; D = D.AddDays(1), R.Days++) ;
if (R.Days > 0) StartDate = StartDate.AddDays(R.Days);
// Calculate Time Stuff
TimeSpan T1 = EndDate - StartDate;
R.Hours = T1.Hours;
R.Minutes = T1.Minutes;
R.Seconds = T1.Seconds;
R.Milliseconds = T1.Milliseconds;
// Return answer. Negate values if the Start Date was later than the End Date
if (Later)
return new DateTimeSpan(-R.Years, -R.Months, -R.Days, -R.Hours, -R.Minutes, -R.Seconds, -R.Milliseconds);
return R;
}
}
Insane method that counts all days, so super precise
helper class :
public class DaysInMonth
{
public int Days { get; set; }
public int Month { get; set; }
public int Year { get; set; }
public bool Full { get; set; }
}
function:
public static List<DaysInMonth> MonthsDelta(DateTime start, DateTime end)
{
var dates = Enumerable.Range(0, 1 + end.Subtract(start).Days)
.Select(offset => start.AddDays(offset))
.ToArray();
DateTime? prev = null;
int days = 0;
List < DaysInMonth > list = new List<DaysInMonth>();
foreach (DateTime date in dates)
{
if (prev != null)
{
if(date.Month!=prev.GetValueOrDefault().Month)
{
DaysInMonth daysInMonth = new DaysInMonth();
daysInMonth.Days = days;
daysInMonth.Month = prev.GetValueOrDefault().Month;
daysInMonth.Year = prev.GetValueOrDefault().Year;
daysInMonth.Full = DateTime.DaysInMonth(daysInMonth.Year, daysInMonth.Month) == daysInMonth.Days;
list.Add(daysInMonth);
days = 0;
}
}
days++;
prev = date;
}
//------------------ add last
if (days > 0)
{
DaysInMonth daysInMonth = new DaysInMonth();
daysInMonth.Days = days;
daysInMonth.Month = prev.GetValueOrDefault().Month;
daysInMonth.Year = prev.GetValueOrDefault().Year;
daysInMonth.Full = DateTime.DaysInMonth(daysInMonth.Year, daysInMonth.Month) == daysInMonth.Days;
list.Add(daysInMonth);
}
return list;
}
Suppose the current quater is 3 and the year is 2011. How can I get the last 5 quarters
Desired output:
Q3-2011
Q2-2011
Q1-2011
Q4-2010
Q3-2010
The Q and '-' is appended.
I am trying as under
int generateQuater = 5;
int currentQuater = 3;//GetQuarter(DateTime.Now.Month);
int currentYear = DateTime.Now.Year;
List<string> lstQuaterYear = new List<string>();
lstQuaterYear.Add(string.Concat('Q',currentQuater, '-', currentYear));
for (int i = generateQuater; i > 0; i++)
{
//code to be placed
}
Thanks
You have to decrease your loop variable. The rest is not too difficult math.
Its also not necessary to handle the first iteration in any special way:
for (int i = generateQuater; i > 0; i--)
{
lstQuaterYear.Add(string.Format("Q{0}-{1}", currentQuater, currentYear));
if (--currentQuater == 0)
{
currentQuater = 4;
currentYear--;
}
}
As a pure LINQ expression:
public IEnumerable<String> GetQuarters(int start, int year, int count)
{
return (from q in Enumerable.Range(0, count)
select String.Format("Q{0}-{1}", (start - q) + (((q + 1) / 4) * 4) , year - ((q + 1) / 4)));
}
The math is somewhat ugly but does work, to use it you can just do:
foreach (String quarter in GetQuarters(3, 2011, 5))
{
Console.WriteLine(quarter);
}
Your for loop should go from 0 to your variable, when you're increasing i.
The inner code could be something like:
currentQuarter--;
if(currentQuarter == 0)
{
currentQuarter = 4;
currentYear--;
}
Don't forget to refactor it :)
int count = 5;
int currentQuarter = GetQuarter(DateTime.Now.Month);
int currentYear = DateTime.Now.Year;
List<string> lstQuaterYear = new List<string>();
for (int i = count; i > 0; i--)
{
lstQuaterYear.Add(string.Concat('Q', currentQuarter, '-', currentYear));
currentQuarter--;
if (currentQuarter == 0)
{
currentQuarter = 4;
currentYear--;
}
}
One way is to check for year roll over and then set the quarter to 4 and decrement the year:
int quarter=3;
int year=2011;
int count=5;
for(int i=0;i<count;i++)
{
lstQuaterYear.Add(string.Format("Q{0} {1}", quarter, year);
quarter--;
if(quarter==0)
{
quarter=4;
year--;
}
}
Alternatively you could calculate a totalQuartal=year+quartal-1. Then decrement it on each step. And finally use year=totalQuartal/4 and quartal=totalQuartal%4+1. But I think the first way is easier to understand.
public static IEnumerable Generate(int number, int currentYear, int currentQuarter)
{
int counter = number;
int quarter = currentQuarter;
int year = currentYear;
while (counter-- > 0)
{
yield return String.Format("Q{0}-{1}", year, quarter);
quarter = quarter>1?quarter-1:4;
year = quarter==4?year-1:year;
}
}
Here is my version (sorry, it is in VB.NET).
The idea is to :
easily find out the quarter based on a date (easy : divide it by 4 ... and add 1 to avoid zeros)
go back in time from the current date, removing 3 month at each time
printout the formatted quarter
the code :
Private Shared Function GetQuarterForDate(ByVal d As DateTime) As Integer
Return (d.Month \ 4) + 1 'integer division
End Function
Private Shared Function GetLastNQuarters(ByVal N As Integer) As IEnumerable(Of String)
Dim myDate = DateTime.Now
Dim res As New List(Of String)()
Do While N > 0
'using yield would be nicer in C# ... does not exist in VB
res.Add(String.Format("Q{0}-{1}", GetQuarterForDate(myDate), myDate.Year))
myDate = myDate.AddMonths(-3)
N = N - 1
Loop
Return res
End Function
<TestMethod()>
Public Sub CanRetrieveQuarter()
Dim quarters = GetLastNQuarters(5)
For Each q In quarters
Console.WriteLine(q)
Next
End Sub
That last "test method" prints out :
Q3-2011
Q2-2011
Q1-2011
Q4-2010
Q3-2010
In case you should do some operations on the quarter period, like check if moment is within a quarter, you can use the Quarter class of the Time Period Library for .NET:
// ----------------------------------------------------------------------
public ITimePeriodCollection GetPastQuarters( int count )
{
TimePeriodCollection quarters = new TimePeriodCollection();
Quarter quarter = new Quarter();
for ( int i = 0; i < count; i++ )
{
quarters.Add( quarter );
quarter = quarter.GetPreviousQuarter();
}
return quarters;
} // GetPastQuarters
How to calculate the difference in months between two dates in C#?
Is there is equivalent of VB's DateDiff() method in C#. I need to find difference in months between two dates that are years apart. The documentation says that I can use TimeSpan like:
TimeSpan ts = date1 - date2;
but this gives me data in Days. I don't want to divide this number by 30 because not every month is 30 days and since the two operand values are quite apart from each other, I am afraid dividing by 30 might give me a wrong value.
Any suggestions?
Assuming the day of the month is irrelevant (i.e. the diff between 2011.1.1 and 2010.12.31 is 1), with date1 > date2 giving a positive value and date2 > date1 a negative value
((date1.Year - date2.Year) * 12) + date1.Month - date2.Month
Or, assuming you want an approximate number of 'average months' between the two dates, the following should work for all but very huge date differences.
date1.Subtract(date2).Days / (365.25 / 12)
Note, if you were to use the latter solution then your unit tests should state the widest date range which your application is designed to work with and validate the results of the calculation accordingly.
Update (with thanks to Gary)
If using the 'average months' method, a slightly more accurate number to use for the 'average number of days per year' is 365.2425.
Here is a comprehensive solution to return a DateTimeSpan, similar to a TimeSpan, except that it includes all the date components in addition to the time components.
Usage:
void Main()
{
DateTime compareTo = DateTime.Parse("8/13/2010 8:33:21 AM");
DateTime now = DateTime.Parse("2/9/2012 10:10:11 AM");
var dateSpan = DateTimeSpan.CompareDates(compareTo, now);
Console.WriteLine("Years: " + dateSpan.Years);
Console.WriteLine("Months: " + dateSpan.Months);
Console.WriteLine("Days: " + dateSpan.Days);
Console.WriteLine("Hours: " + dateSpan.Hours);
Console.WriteLine("Minutes: " + dateSpan.Minutes);
Console.WriteLine("Seconds: " + dateSpan.Seconds);
Console.WriteLine("Milliseconds: " + dateSpan.Milliseconds);
}
Outputs:
Years: 1
Months: 5
Days: 27
Hours: 1
Minutes: 36
Seconds: 50
Milliseconds: 0
For convenience, I've lumped the logic into the DateTimeSpan struct, but you may move the method CompareDates wherever you see fit. Also note, it doesn't matter which date comes before the other.
public struct DateTimeSpan
{
public int Years { get; }
public int Months { get; }
public int Days { get; }
public int Hours { get; }
public int Minutes { get; }
public int Seconds { get; }
public int Milliseconds { get; }
public DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)
{
Years = years;
Months = months;
Days = days;
Hours = hours;
Minutes = minutes;
Seconds = seconds;
Milliseconds = milliseconds;
}
enum Phase { Years, Months, Days, Done }
public static DateTimeSpan CompareDates(DateTime date1, DateTime date2)
{
if (date2 < date1)
{
var sub = date1;
date1 = date2;
date2 = sub;
}
DateTime current = date1;
int years = 0;
int months = 0;
int days = 0;
Phase phase = Phase.Years;
DateTimeSpan span = new DateTimeSpan();
int officialDay = current.Day;
while (phase != Phase.Done)
{
switch (phase)
{
case Phase.Years:
if (current.AddYears(years + 1) > date2)
{
phase = Phase.Months;
current = current.AddYears(years);
}
else
{
years++;
}
break;
case Phase.Months:
if (current.AddMonths(months + 1) > date2)
{
phase = Phase.Days;
current = current.AddMonths(months);
if (current.Day < officialDay && officialDay <= DateTime.DaysInMonth(current.Year, current.Month))
current = current.AddDays(officialDay - current.Day);
}
else
{
months++;
}
break;
case Phase.Days:
if (current.AddDays(days + 1) > date2)
{
current = current.AddDays(days);
var timespan = date2 - current;
span = new DateTimeSpan(years, months, days, timespan.Hours, timespan.Minutes, timespan.Seconds, timespan.Milliseconds);
phase = Phase.Done;
}
else
{
days++;
}
break;
}
}
return span;
}
}
You could do
if ( date1.AddMonths(x) > date2 )
If you want the exact number of full months, always positive (2000-01-15, 2000-02-14 returns 0), considering a full month is when you reach the same day the next month (something like the age calculation)
public static int GetMonthsBetween(DateTime from, DateTime to)
{
if (from > to) return GetMonthsBetween(to, from);
var monthDiff = Math.Abs((to.Year * 12 + (to.Month - 1)) - (from.Year * 12 + (from.Month - 1)));
if (from.AddMonths(monthDiff) > to || to.Day < from.Day)
{
return monthDiff - 1;
}
else
{
return monthDiff;
}
}
Edit reason: the old code was not correct in some cases like :
new { From = new DateTime(1900, 8, 31), To = new DateTime(1901, 8, 30), Result = 11 },
Test cases I used to test the function:
var tests = new[]
{
new { From = new DateTime(1900, 1, 1), To = new DateTime(1900, 1, 1), Result = 0 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1900, 1, 2), Result = 0 },
new { From = new DateTime(1900, 1, 2), To = new DateTime(1900, 1, 1), Result = 0 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1900, 2, 1), Result = 1 },
new { From = new DateTime(1900, 2, 1), To = new DateTime(1900, 1, 1), Result = 1 },
new { From = new DateTime(1900, 1, 31), To = new DateTime(1900, 2, 1), Result = 0 },
new { From = new DateTime(1900, 8, 31), To = new DateTime(1900, 9, 30), Result = 0 },
new { From = new DateTime(1900, 8, 31), To = new DateTime(1900, 10, 1), Result = 1 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1901, 1, 1), Result = 12 },
new { From = new DateTime(1900, 1, 1), To = new DateTime(1911, 1, 1), Result = 132 },
new { From = new DateTime(1900, 8, 31), To = new DateTime(1901, 8, 30), Result = 11 },
};
I checked the usage of this method in VB.NET via MSDN and it seems that it has a lot of usages. There is no such a built-in method in C#. (Even it's not a good idea) you can call VB's in C#.
Add Microsoft.VisualBasic.dll to
your project as a reference
use
Microsoft.VisualBasic.DateAndTime.DateDiff
in your code
Use Noda Time:
LocalDate start = new LocalDate(2013, 1, 5);
LocalDate end = new LocalDate(2014, 6, 1);
Period period = Period.Between(start, end, PeriodUnits.Months);
Console.WriteLine(period.Months); // 16
(example source)
To get difference in months (both start and end inclusive), irrespective of dates:
DateTime start = new DateTime(2013, 1, 1);
DateTime end = new DateTime(2014, 2, 1);
var diffMonths = (end.Month + end.Year * 12) - (start.Month + start.Year * 12);
I just needed something simple to cater for e.g. employment dates where only the month/year is entered, so wanted distinct years and months worked in. This is what I use, here for usefullness only
public static YearsMonths YearMonthDiff(DateTime startDate, DateTime endDate) {
int monthDiff = ((endDate.Year * 12) + endDate.Month) - ((startDate.Year * 12) + startDate.Month) + 1;
int years = (int)Math.Floor((decimal) (monthDiff / 12));
int months = monthDiff % 12;
return new YearsMonths {
TotalMonths = monthDiff,
Years = years,
Months = months
};
}
.NET Fiddle
You can use Noda Time https://nodatime.org/
LocalDate start = new LocalDate(2010, 1, 5);
LocalDate end = new LocalDate(2012, 6, 1);
Period period = Period.Between(start, end, PeriodUnits.Months);
Console.WriteLine(period.Months);
You can use the DateDiff class of the Time Period Library for .NET:
// ----------------------------------------------------------------------
public void DateDiffSample()
{
DateTime date1 = new DateTime( 2009, 11, 8, 7, 13, 59 );
DateTime date2 = new DateTime( 2011, 3, 20, 19, 55, 28 );
DateDiff dateDiff = new DateDiff( date1, date2 );
// differences
Console.WriteLine( "DateDiff.Months: {0}", dateDiff.Months );
// > DateDiff.Months: 16
// elapsed
Console.WriteLine( "DateDiff.ElapsedMonths: {0}", dateDiff.ElapsedMonths );
// > DateDiff.ElapsedMonths: 4
// description
Console.WriteLine( "DateDiff.GetDescription(6): {0}", dateDiff.GetDescription( 6 ) );
// > DateDiff.GetDescription(6): 1 Year 4 Months 12 Days 12 Hours 41 Mins 29 Secs
} // DateDiffSample
Here is my contribution to get difference in Months that I've found to be accurate:
namespace System
{
public static class DateTimeExtensions
{
public static Int32 DiffMonths( this DateTime start, DateTime end )
{
Int32 months = 0;
DateTime tmp = start;
while ( tmp < end )
{
months++;
tmp = tmp.AddMonths( 1 );
}
return months;
}
}
}
Usage:
Int32 months = DateTime.Now.DiffMonths( DateTime.Now.AddYears( 5 ) );
You can create another method called DiffYears and apply exactly the same logic as above and AddYears instead of AddMonths in the while loop.
This worked for what I needed it for. The day of month didn't matter in my case because it always happens to be the last day of the month.
public static int MonthDiff(DateTime d1, DateTime d2){
int retVal = 0;
if (d1.Month<d2.Month)
{
retVal = (d1.Month + 12) - d2.Month;
retVal += ((d1.Year - 1) - d2.Year)*12;
}
else
{
retVal = d1.Month - d2.Month;
retVal += (d1.Year - d2.Year)*12;
}
//// Calculate the number of years represented and multiply by 12
//// Substract the month number from the total
//// Substract the difference of the second month and 12 from the total
//retVal = (d1.Year - d2.Year) * 12;
//retVal = retVal - d1.Month;
//retVal = retVal - (12 - d2.Month);
return retVal;
}
There's 3 cases: same year, previous year and other years.
If the day of the month does not matter...
public int GetTotalNumberOfMonths(DateTime start, DateTime end)
{
// work with dates in the right order
if (start > end)
{
var swapper = start;
start = end;
end = swapper;
}
switch (end.Year - start.Year)
{
case 0: // Same year
return end.Month - start.Month;
case 1: // last year
return (12 - start.Month) + end.Month;
default:
return 12 * (3 - (end.Year - start.Year)) + (12 - start.Month) + end.Month;
}
}
The most precise way is this that return difference in months by fraction :
private double ReturnDiffereceBetweenTwoDatesInMonths(DateTime startDateTime, DateTime endDateTime)
{
double result = 0;
double days = 0;
DateTime currentDateTime = startDateTime;
while (endDateTime > currentDateTime.AddMonths(1))
{
result ++;
currentDateTime = currentDateTime.AddMonths(1);
}
if (endDateTime > currentDateTime)
{
days = endDateTime.Subtract(currentDateTime).TotalDays;
}
return result + days/endDateTime.GetMonthDays;
}
My understanding of the total months difference between 2 dates has an integral and a fractional part (the date matters).
The integral part is the full months difference.
The fractional part, for me, is the difference of the % of the day (to the full days of month) between the starting and ending months.
public static class DateTimeExtensions
{
public static double TotalMonthsDifference(this DateTime from, DateTime to)
{
//Compute full months difference between dates
var fullMonthsDiff = (to.Year - from.Year)*12 + to.Month - from.Month;
//Compute difference between the % of day to full days of each month
var fractionMonthsDiff = ((double)(to.Day-1) / (DateTime.DaysInMonth(to.Year, to.Month)-1)) -
((double)(from.Day-1)/ (DateTime.DaysInMonth(from.Year, from.Month)-1));
return fullMonthsDiff + fractionMonthsDiff;
}
}
With this extension, those are the results:
2/29/2000 TotalMonthsDifference 2/28/2001 => 12
2/28/2000 TotalMonthsDifference 2/28/2001 => 12.035714285714286
01/01/2000 TotalMonthsDifference 01/16/2000 => 0.5
01/31/2000 TotalMonthsDifference 01/01/2000 => -1.0
01/31/2000 TotalMonthsDifference 02/29/2000 => 1.0
01/31/2000 TotalMonthsDifference 02/28/2000 => 0.9642857142857143
01/31/2001 TotalMonthsDifference 02/28/2001 => 1.0
Here is a simple solution that works at least for me. It's probably not the fastest though because it uses the cool DateTime's AddMonth feature in a loop:
public static int GetMonthsDiff(DateTime start, DateTime end)
{
if (start > end)
return GetMonthsDiff(end, start);
int months = 0;
do
{
start = start.AddMonths(1);
if (start > end)
return months;
months++;
}
while (true);
}
This simple static function calculates the fraction of months between two Datetimes, e.g.
1.1. to 31.1. = 1.0
1.4. to 15.4. = 0.5
16.4. to 30.4. = 0.5
1.3. to 1.4. = 1 + 1/30
The function assumes that the first date is smaller than the second date. To deal with negative time intervals one can modify the function easily by introducing a sign and a variable swap at the beginning.
public static double GetDeltaMonths(DateTime t0, DateTime t1)
{
DateTime t = t0;
double months = 0;
while(t<=t1)
{
int daysInMonth = DateTime.DaysInMonth(t.Year, t.Month);
DateTime endOfMonth = new DateTime(t.Year, t.Month, daysInMonth);
int cutDay = endOfMonth <= t1 ? daysInMonth : t1.Day;
months += (cutDay - t.Day + 1) / (double) daysInMonth;
t = new DateTime(t.Year, t.Month, 1).AddMonths(1);
}
return Math.Round(months,2);
}
one line solution
For first, check if both dates are in the current year, if not get months of whole years and then add months from the start and end year.
DateTime dateFrom = new DateTime(2019, 2, 1);
DateTime dateTo = new DateTime(2021, 5, 25);
With the first month
var monthCount = dateFrom.Year != dateTo.Year ? ((dateTo.Year - dateFrom.Year - 1) * 12) + (13 - dateFrom.Month + dateTo.Month) : dateTo.Month - dateFrom.Month + 1;
result = 28
Without first month
monthCount = dateFrom.Year != dateTo.Year ? ((dateTo.Year - dateFrom.Year - 1) * 12) + (12 - dateFrom.Month + dateTo.Month) : dateTo.Month - dateFrom.Month;
result = 27
Public Class ClassDateOperation
Private prop_DifferenceInDay As Integer
Private prop_DifferenceInMonth As Integer
Private prop_DifferenceInYear As Integer
Public Function DayMonthYearFromTwoDate(ByVal DateStart As Date, ByVal DateEnd As Date) As ClassDateOperation
Dim differenceInDay As Integer
Dim differenceInMonth As Integer
Dim differenceInYear As Integer
Dim myDate As Date
DateEnd = DateEnd.AddDays(1)
differenceInYear = DateEnd.Year - DateStart.Year
If DateStart.Month <= DateEnd.Month Then
differenceInMonth = DateEnd.Month - DateStart.Month
Else
differenceInYear -= 1
differenceInMonth = (12 - DateStart.Month) + DateEnd.Month
End If
If DateStart.Day <= DateEnd.Day Then
differenceInDay = DateEnd.Day - DateStart.Day
Else
myDate = CDate("01/" & DateStart.AddMonths(1).Month & "/" & DateStart.Year).AddDays(-1)
If differenceInMonth <> 0 Then
differenceInMonth -= 1
Else
differenceInMonth = 11
differenceInYear -= 1
End If
differenceInDay = myDate.Day - DateStart.Day + DateEnd.Day
End If
prop_DifferenceInDay = differenceInDay
prop_DifferenceInMonth = differenceInMonth
prop_DifferenceInYear = differenceInYear
Return Me
End Function
Public ReadOnly Property DifferenceInDay() As Integer
Get
Return prop_DifferenceInDay
End Get
End Property
Public ReadOnly Property DifferenceInMonth As Integer
Get
Return prop_DifferenceInMonth
End Get
End Property
Public ReadOnly Property DifferenceInYear As Integer
Get
Return prop_DifferenceInYear
End Get
End Property
End Class
This is from my own library, will return the difference of months between two dates.
public static int MonthDiff(DateTime d1, DateTime d2)
{
int retVal = 0;
// Calculate the number of years represented and multiply by 12
// Substract the month number from the total
// Substract the difference of the second month and 12 from the total
retVal = (d1.Year - d2.Year) * 12;
retVal = retVal - d1.Month;
retVal = retVal - (12 - d2.Month);
return retVal;
}
You can have a function something like this.
For Example, from 2012/12/27 to 2012/12/29 becomes 3 days. Likewise, from 2012/12/15 to 2013/01/15 becomes 2 months, because up to 2013/01/14 it's 1 month. from 15th it's 2nd month started.
You can remove the "=" in the second if condition, if you do not want to include both days in the calculation. i.e, from 2012/12/15 to 2013/01/15 is 1 month.
public int GetMonths(DateTime startDate, DateTime endDate)
{
if (startDate > endDate)
{
throw new Exception("Start Date is greater than the End Date");
}
int months = ((endDate.Year * 12) + endDate.Month) - ((startDate.Year * 12) + startDate.Month);
if (endDate.Day >= startDate.Day)
{
months++;
}
return months;
}
you can use the following extension:
Code
public static class Ext
{
#region Public Methods
public static int GetAge(this DateTime #this)
{
var today = DateTime.Today;
return ((((today.Year - #this.Year) * 100) + (today.Month - #this.Month)) * 100 + today.Day - #this.Day) / 10000;
}
public static int DiffMonths(this DateTime #from, DateTime #to)
{
return (((((#to.Year - #from.Year) * 12) + (#to.Month - #from.Month)) * 100 + #to.Day - #from.Day) / 100);
}
public static int DiffYears(this DateTime #from, DateTime #to)
{
return ((((#to.Year - #from.Year) * 100) + (#to.Month - #from.Month)) * 100 + #to.Day - #from.Day) / 10000;
}
#endregion Public Methods
}
Implementation !
int Age;
int years;
int Months;
//Replace your own date
var d1 = new DateTime(2000, 10, 22);
var d2 = new DateTime(2003, 10, 20);
//Age
Age = d1.GetAge();
Age = d2.GetAge();
//positive
years = d1.DiffYears(d2);
Months = d1.DiffMonths(d2);
//negative
years = d2.DiffYears(d1);
Months = d2.DiffMonths(d1);
//Or
Months = Ext.DiffMonths(d1, d2);
years = Ext.DiffYears(d1, d2);
Here's a much more concise solution using VB.Net DateDiff for Year, Month, Day only. You can load the DateDiff library in C# as well.
date1 must be <= date2
VB.NET
Dim date1 = Now.AddDays(-2000)
Dim date2 = Now
Dim diffYears = DateDiff(DateInterval.Year, date1, date2) - If(date1.DayOfYear > date2.DayOfYear, 1, 0)
Dim diffMonths = DateDiff(DateInterval.Month, date1, date2) - diffYears * 12 - If(date1.Day > date2.Day, 1, 0)
Dim diffDays = If(date2.Day >= date1.Day, date2.Day - date1.Day, date2.Day + (Date.DaysInMonth(date1.Year, date1.Month) - date1.Day))
C#
DateTime date1 = Now.AddDays(-2000);
DateTime date2 = Now;
int diffYears = DateDiff(DateInterval.Year, date1, date2) - date1.DayOfYear > date2.DayOfYear ? 1 : 0;
int diffMonths = DateDiff(DateInterval.Month, date1, date2) - diffYears * 12 - date1.Day > date2.Day ? 1 : 0;
int diffDays = date2.Day >= date1.Day ? date2.Day - date1.Day : date2.Day + (System.DateTime.DaysInMonth(date1.Year, date1.Month) - date1.Day);
This is in response to Kirk Woll's answer. I don't have enough reputation points to reply to a comment yet...
I liked Kirk's solution and was going to shamelessly rip it off and use it in my code, but when I looked through it I realized it's way too complicated. Unnecessary switching and looping, and a public constructor that is pointless to use.
Here's my rewrite:
public class DateTimeSpan {
private DateTime _date1;
private DateTime _date2;
private int _years;
private int _months;
private int _days;
private int _hours;
private int _minutes;
private int _seconds;
private int _milliseconds;
public int Years { get { return _years; } }
public int Months { get { return _months; } }
public int Days { get { return _days; } }
public int Hours { get { return _hours; } }
public int Minutes { get { return _minutes; } }
public int Seconds { get { return _seconds; } }
public int Milliseconds { get { return _milliseconds; } }
public DateTimeSpan(DateTime date1, DateTime date2) {
_date1 = (date1 > date2) ? date1 : date2;
_date2 = (date2 < date1) ? date2 : date1;
_years = _date1.Year - _date2.Year;
_months = (_years * 12) + _date1.Month - _date2.Month;
TimeSpan t = (_date2 - _date1);
_days = t.Days;
_hours = t.Hours;
_minutes = t.Minutes;
_seconds = t.Seconds;
_milliseconds = t.Milliseconds;
}
public static DateTimeSpan CompareDates(DateTime date1, DateTime date2) {
return new DateTimeSpan(date1, date2);
}
}
Usage1, pretty much the same:
void Main()
{
DateTime compareTo = DateTime.Parse("8/13/2010 8:33:21 AM");
DateTime now = DateTime.Parse("2/9/2012 10:10:11 AM");
var dateSpan = new DateTimeSpan(compareTo, now);
Console.WriteLine("Years: " + dateSpan.Years);
Console.WriteLine("Months: " + dateSpan.Months);
Console.WriteLine("Days: " + dateSpan.Days);
Console.WriteLine("Hours: " + dateSpan.Hours);
Console.WriteLine("Minutes: " + dateSpan.Minutes);
Console.WriteLine("Seconds: " + dateSpan.Seconds);
Console.WriteLine("Milliseconds: " + dateSpan.Milliseconds);
}
Usage2, similar:
void Main()
{
DateTime compareTo = DateTime.Parse("8/13/2010 8:33:21 AM");
DateTime now = DateTime.Parse("2/9/2012 10:10:11 AM");
Console.WriteLine("Years: " + DateTimeSpan.CompareDates(compareTo, now).Years);
Console.WriteLine("Months: " + DateTimeSpan.CompareDates(compareTo, now).Months);
Console.WriteLine("Days: " + DateTimeSpan.CompareDates(compareTo, now).Days);
Console.WriteLine("Hours: " + DateTimeSpan.CompareDates(compareTo, now).Hours);
Console.WriteLine("Minutes: " + DateTimeSpan.CompareDates(compareTo, now).Minutes);
Console.WriteLine("Seconds: " + DateTimeSpan.CompareDates(compareTo, now).Seconds);
Console.WriteLine("Milliseconds: " + DateTimeSpan.CompareDates(compareTo, now).Milliseconds);
}
In my case it is required to calculate the complete month from the start date to the day prior to this day in the next month or from start to end of month.
Ex: from 1/1/2018 to 31/1/2018 is a complete month
Ex2: from 5/1/2018 to 4/2/2018 is a complete month
so based on this here is my solution:
public static DateTime GetMonthEnd(DateTime StartDate, int MonthsCount = 1)
{
return StartDate.AddMonths(MonthsCount).AddDays(-1);
}
public static Tuple<int, int> CalcPeriod(DateTime StartDate, DateTime EndDate)
{
int MonthsCount = 0;
Tuple<int, int> Period;
while (true)
{
if (GetMonthEnd(StartDate) > EndDate)
break;
else
{
MonthsCount += 1;
StartDate = StartDate.AddMonths(1);
}
}
int RemainingDays = (EndDate - StartDate).Days + 1;
Period = new Tuple<int, int>(MonthsCount, RemainingDays);
return Period;
}
Usage:
Tuple<int, int> Period = CalcPeriod(FromDate, ToDate);
Note: in my case it was required to calculate the remaining days after the complete months so if it's not your case you could ignore the days result or even you could change the method return from tuple to integer.
public static int PayableMonthsInDuration(DateTime StartDate, DateTime EndDate)
{
int sy = StartDate.Year; int sm = StartDate.Month; int count = 0;
do
{
count++;if ((sy == EndDate.Year) && (sm >= EndDate.Month)) { break; }
sm++;if (sm == 13) { sm = 1; sy++; }
} while ((EndDate.Year >= sy) || (EndDate.Month >= sm));
return (count);
}
This solution is for Rental/subscription calculation, where difference doesn't means to be subtraction, it's meant to be the span in within those two dates.
I wrote a function to accomplish this, because the others ways weren't working for me.
public string getEndDate (DateTime startDate,decimal monthCount)
{
int y = startDate.Year;
int m = startDate.Month;
for (decimal i = monthCount; i > 1; i--)
{
m++;
if (m == 12)
{ y++;
m = 1;
}
}
return string.Format("{0}-{1}-{2}", y.ToString(), m.ToString(), startDate.Day.ToString());
}
There are not a lot of clear answers on this because you are always assuming things.
This solution calculates between two dates the months between assuming you want to save the day of month for comparison, (meaning that the day of the month is considered in the calculation)
Example, if you have a date of 30 Jan 2012, 29 Feb 2012 will not be a month but 01 March 2013 will.
It's been tested pretty thoroughly, probably will clean it up later as we use it, but here:
private static int TotalMonthDifference(DateTime dtThis, DateTime dtOther)
{
int intReturn = 0;
bool sameMonth = false;
if (dtOther.Date < dtThis.Date) //used for an error catch in program, returns -1
intReturn--;
int dayOfMonth = dtThis.Day; //captures the month of day for when it adds a month and doesn't have that many days
int daysinMonth = 0; //used to caputre how many days are in the month
while (dtOther.Date > dtThis.Date) //while Other date is still under the other
{
dtThis = dtThis.AddMonths(1); //as we loop, we just keep adding a month for testing
daysinMonth = DateTime.DaysInMonth(dtThis.Year, dtThis.Month); //grabs the days in the current tested month
if (dtThis.Day != dayOfMonth) //Example 30 Jan 2013 will go to 28 Feb when a month is added, so when it goes to march it will be 28th and not 30th
{
if (daysinMonth < dayOfMonth) // uses day in month max if can't set back to day of month
dtThis.AddDays(daysinMonth - dtThis.Day);
else
dtThis.AddDays(dayOfMonth - dtThis.Day);
}
if (((dtOther.Year == dtThis.Year) && (dtOther.Month == dtThis.Month))) //If the loop puts it in the same month and year
{
if (dtOther.Day >= dayOfMonth) //check to see if it is the same day or later to add one to month
intReturn++;
sameMonth = true; //sets this to cancel out of the normal counting of month
}
if ((!sameMonth)&&(dtOther.Date > dtThis.Date))//so as long as it didn't reach the same month (or if i started in the same month, one month ahead, add a month)
intReturn++;
}
return intReturn; //return month
}
Based on the excellent DateTimeSpan work done above, I've normalized the code a bit; this seems to work pretty well:
public class DateTimeSpan
{
private DateTimeSpan() { }
private DateTimeSpan(int years, int months, int days, int hours, int minutes, int seconds, int milliseconds)
{
Years = years;
Months = months;
Days = days;
Hours = hours;
Minutes = minutes;
Seconds = seconds;
Milliseconds = milliseconds;
}
public int Years { get; private set; } = 0;
public int Months { get; private set; } = 0;
public int Days { get; private set; } = 0;
public int Hours { get; private set; } = 0;
public int Minutes { get; private set; } = 0;
public int Seconds { get; private set; } = 0;
public int Milliseconds { get; private set; } = 0;
public static DateTimeSpan CompareDates(DateTime StartDate, DateTime EndDate)
{
if (StartDate.Equals(EndDate)) return new DateTimeSpan();
DateTimeSpan R = new DateTimeSpan();
bool Later;
if (Later = StartDate > EndDate)
{
DateTime D = StartDate;
StartDate = EndDate;
EndDate = D;
}
// Calculate Date Stuff
for (DateTime D = StartDate.AddYears(1); D < EndDate; D = D.AddYears(1), R.Years++) ;
if (R.Years > 0) StartDate = StartDate.AddYears(R.Years);
for (DateTime D = StartDate.AddMonths(1); D < EndDate; D = D.AddMonths(1), R.Months++) ;
if (R.Months > 0) StartDate = StartDate.AddMonths(R.Months);
for (DateTime D = StartDate.AddDays(1); D < EndDate; D = D.AddDays(1), R.Days++) ;
if (R.Days > 0) StartDate = StartDate.AddDays(R.Days);
// Calculate Time Stuff
TimeSpan T1 = EndDate - StartDate;
R.Hours = T1.Hours;
R.Minutes = T1.Minutes;
R.Seconds = T1.Seconds;
R.Milliseconds = T1.Milliseconds;
// Return answer. Negate values if the Start Date was later than the End Date
if (Later)
return new DateTimeSpan(-R.Years, -R.Months, -R.Days, -R.Hours, -R.Minutes, -R.Seconds, -R.Milliseconds);
return R;
}
}
Insane method that counts all days, so super precise
helper class :
public class DaysInMonth
{
public int Days { get; set; }
public int Month { get; set; }
public int Year { get; set; }
public bool Full { get; set; }
}
function:
public static List<DaysInMonth> MonthsDelta(DateTime start, DateTime end)
{
var dates = Enumerable.Range(0, 1 + end.Subtract(start).Days)
.Select(offset => start.AddDays(offset))
.ToArray();
DateTime? prev = null;
int days = 0;
List < DaysInMonth > list = new List<DaysInMonth>();
foreach (DateTime date in dates)
{
if (prev != null)
{
if(date.Month!=prev.GetValueOrDefault().Month)
{
DaysInMonth daysInMonth = new DaysInMonth();
daysInMonth.Days = days;
daysInMonth.Month = prev.GetValueOrDefault().Month;
daysInMonth.Year = prev.GetValueOrDefault().Year;
daysInMonth.Full = DateTime.DaysInMonth(daysInMonth.Year, daysInMonth.Month) == daysInMonth.Days;
list.Add(daysInMonth);
days = 0;
}
}
days++;
prev = date;
}
//------------------ add last
if (days > 0)
{
DaysInMonth daysInMonth = new DaysInMonth();
daysInMonth.Days = days;
daysInMonth.Month = prev.GetValueOrDefault().Month;
daysInMonth.Year = prev.GetValueOrDefault().Year;
daysInMonth.Full = DateTime.DaysInMonth(daysInMonth.Year, daysInMonth.Month) == daysInMonth.Days;
list.Add(daysInMonth);
}
return list;
}
I've got the Day of the week stored in a database table (that I do not control), and I need to use it in my code.
Problem is, I want to use the System.DayOfWeek enum for representation for this, and the sequences are not the same.
In the database, it's as follows:
1 2 3 4 5 6 7
S M T W T F S
I need it as follows:
0 1 2 3 4 5 6
M T W T F S S
What's the most elegant way to do this?
for example, I could do:
i = dayOfWeek;
i = i - 2;
if (i < 0) {
i = 6;
}
but that's a bit inelegant. Any suggestions?
<EDIT>
Ahem. Apparently (.net reflector says) DayOfWeek is 0 indexed starting with Sunday.
Always read the docs before asking daft questions.
However, I'm still interested in an answer, just to satisfy my own curiosity, so go for it.
</EDIT>
The value you want is
(DayOfWeek)((dbDay + 5) % 7)
using the modulo operator %.
Wrap it in a function:
public int DbToDayOfWeek(int dbDay)
{
if (dbDay == 1)
return 6;
return dbDay -2;
}
Or:
public DayOfWeek DbToDayOfWeek(int dbDay)
{
if (dbDay == 1)
return DayOfWeek.Sunday;
return (DayOfWeek)(dbDay - 2);
}
Although I can't imagine the values changing, you should really avoid assuming that the DayOfWeek enumerated values will stay the same - so code accordingly.
static DayOfWeek[] _toDaysTable = new DayOfWeek[] {
DayOfWeek.Sunday, DayOfWeek.Monday, DayOfWeek.Tuesday, DayOfWeek.Wednesday,
DayOfWeek.Thursday, DayOfWeek.Friday, DayOfWeek.Saturday
};
static DayOfWeek ToDayOfWeek(int myDayOfWeek)
{
int index = myDayOfWeek - 1;
if (index < 0 || index >= _toDaysTable.Length)
throw new ArgumentOutOfRangeException("myDayOfWeek");
return _toDaysTable[index];
}
static int FromDayOfWeek(DayOfWeek day)
{
int index = Array.IndexOf(_toDaysTable, day);
if (index < 0)
throw new ArgumentOutOfRangeException("day");
return index + 1;
}
You could just create your own enum and map the enum directly to the value in the database
public enum DayOfWeek
{
Mon = 2,
Tue = 3,
Wed = 4,
Thu = 5,
Fri = 6,
Sat = 7,
Sun = 1
}
Then you could use an extension method of your DayOfWeek type to retrieve the value:
public static int ToInt(this DayOfWeek dow)
{
return (int)dow;
}
Unless you are relying on the DayOfWeek for actual comparisons with Dates, otherwise you will have to do the conversion between the offsets.