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How do I calculate someone's age based on a DateTime type birthday?
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Closed 6 years ago.
How can I calculate date difference between two dates in years?
For example: (Datetime.Now.Today() - 11/03/2007) in years.
I have written an implementation that properly works with dates exactly one year apart.
However, it does not gracefully handle negative timespans, unlike the other algorithm. It also doesn't use its own date arithmetic, instead relying upon the standard library for that.
So without further ado, here is the code:
DateTime zeroTime = new DateTime(1, 1, 1);
DateTime a = new DateTime(2007, 1, 1);
DateTime b = new DateTime(2008, 1, 1);
TimeSpan span = b - a;
// Because we start at year 1 for the Gregorian
// calendar, we must subtract a year here.
int years = (zeroTime + span).Year - 1;
// 1, where my other algorithm resulted in 0.
Console.WriteLine("Yrs elapsed: " + years);
Use:
int Years(DateTime start, DateTime end)
{
return (end.Year - start.Year - 1) +
(((end.Month > start.Month) ||
((end.Month == start.Month) && (end.Day >= start.Day))) ? 1 : 0);
}
We had to code a check to establish if the difference between two dates, a start and end date was greater than 2 years.
Thanks to the tips above it was done as follows:
DateTime StartDate = Convert.ToDateTime("01/01/2012");
DateTime EndDate = Convert.ToDateTime("01/01/2014");
DateTime TwoYears = StartDate.AddYears(2);
if EndDate > TwoYears .....
If you need it for knowing someone's age for trivial reasons then Timespan is OK but if you need for calculating superannuation, long term deposits or anything else for financial, scientific or legal purposes then I'm afraid Timespan won't be accurate enough because Timespan assumes that every year has the same number of days, same # of hours and same # of seconds).
In reality the length of some years will vary (for different reasons that are outside the scope of this answer). To get around Timespan's limitation then you can mimic what Excel does which is:
public int GetDifferenceInYears(DateTime startDate, DateTime endDate)
{
//Excel documentation says "COMPLETE calendar years in between dates"
int years = endDate.Year - startDate.Year;
if (startDate.Month == endDate.Month &&// if the start month and the end month are the same
endDate.Day < startDate.Day// AND the end day is less than the start day
|| endDate.Month < startDate.Month)// OR if the end month is less than the start month
{
years--;
}
return years;
}
var totalYears =
(DateTime.Today - new DateTime(2007, 03, 11)).TotalDays
/ 365.2425;
Average days from Wikipedia/Leap_year.
int Age = new DateTime((DateTime.Now - BirthDateTime).Ticks).Year;
To calculate the elapsed years (age), the result will be minus one.
var timeSpan = DateTime.Now - birthDateTime;
int age = new DateTime(timeSpan.Ticks).Year - 1;
Here is a neat trick which lets the system deal with leap years automagically. It gives an accurate answer for all date combinations.
DateTime dt1 = new DateTime(1987, 9, 23, 13, 12, 12, 0);
DateTime dt2 = new DateTime(2007, 6, 15, 16, 25, 46, 0);
DateTime tmp = dt1;
int years = -1;
while (tmp < dt2)
{
years++;
tmp = tmp.AddYears(1);
}
Console.WriteLine("{0}", years);
It's unclear how you want to handle fractional years, but perhaps like this:
DateTime now = DateTime.Now;
DateTime origin = new DateTime(2007, 11, 3);
int calendar_years = now.Year - origin.Year;
int whole_years = calendar_years - ((now.AddYears(-calendar_years) >= origin)? 0: 1);
int another_method = calendar_years - ((now.Month - origin.Month) * 32 >= origin.Day - now.Day)? 0: 1);
I implemented an extension method to get the number of years between two dates, rounded by whole months.
/// <summary>
/// Gets the total number of years between two dates, rounded to whole months.
/// Examples:
/// 2011-12-14, 2012-12-15 returns 1.
/// 2011-12-14, 2012-12-14 returns 1.
/// 2011-12-14, 2012-12-13 returns 0,9167.
/// </summary>
/// <param name="start">
/// Stardate of time period
/// </param>
/// <param name="end">
/// Enddate of time period
/// </param>
/// <returns>
/// Total Years between the two days
/// </returns>
public static double DifferenceTotalYears(this DateTime start, DateTime end)
{
// Get difference in total months.
int months = ((end.Year - start.Year) * 12) + (end.Month - start.Month);
// substract 1 month if end month is not completed
if (end.Day < start.Day)
{
months--;
}
double totalyears = months / 12d;
return totalyears;
}
public string GetAgeText(DateTime birthDate)
{
const double ApproxDaysPerMonth = 30.4375;
const double ApproxDaysPerYear = 365.25;
int iDays = (DateTime.Now - birthDate).Days;
int iYear = (int)(iDays / ApproxDaysPerYear);
iDays -= (int)(iYear * ApproxDaysPerYear);
int iMonths = (int)(iDays / ApproxDaysPerMonth);
iDays -= (int)(iMonths * ApproxDaysPerMonth);
return string.Format("{0} år, {1} måneder, {2} dage", iYear, iMonths, iDays);
}
I found this at TimeSpan for years, months and days:
DateTime target_dob = THE_DOB;
DateTime true_age = DateTime.MinValue + ((TimeSpan)(DateTime.Now - target_dob )); // Minimum value as 1/1/1
int yr = true_age.Year - 1;
If you're dealing with months and years you need something that knows how many days each month has and which years are leap years.
Enter the Gregorian Calendar (and other culture-specific Calendar implementations).
While Calendar doesn't provide methods to directly calculate the difference between two points in time, it does have methods such as
DateTime AddWeeks(DateTime time, int weeks)
DateTime AddMonths(DateTime time, int months)
DateTime AddYears(DateTime time, int years)
DateTime musteriDogum = new DateTime(dogumYil, dogumAy, dogumGun);
int additionalDays = ((DateTime.Now.Year - dogumYil) / 4); //Count of the years with 366 days
int extraDays = additionalDays + ((DateTime.Now.Year % 4 == 0 || musteriDogum.Year % 4 == 0) ? 1 : 0); //We add 1 if this year or year inserted has 366 days
int yearsOld = ((DateTime.Now - musteriDogum).Days - extraDays ) / 365; // Now we extract these extra days from total days and we can divide to 365
Works perfect:
internal static int GetDifferenceInYears(DateTime startDate)
{
int finalResult = 0;
const int DaysInYear = 365;
DateTime endDate = DateTime.Now;
TimeSpan timeSpan = endDate - startDate;
if (timeSpan.TotalDays > 365)
{
finalResult = (int)Math.Round((timeSpan.TotalDays / DaysInYear), MidpointRounding.ToEven);
}
return finalResult;
}
Simple solution:
public int getYearDiff(DateTime startDate, DateTime endDate){
int y = Year(endDate) - Year(startDate);
int startMonth = Month(startDate);
int endMonth = Month(endDate);
if (endMonth < startMonth)
return y - 1;
if (endMonth > startMonth)
return y;
return (Day(endDate) < Day(startDate) ? y - 1 : y);
}
This is the best code to calculate year and month difference:
DateTime firstDate = DateTime.Parse("1/31/2019");
DateTime secondDate = DateTime.Parse("2/1/2016");
int totalYears = firstDate.Year - secondDate.Year;
int totalMonths = 0;
if (firstDate.Month > secondDate.Month)
totalMonths = firstDate.Month - secondDate.Month;
else if (firstDate.Month < secondDate.Month)
{
totalYears -= 1;
int monthDifference = secondDate.Month - firstDate.Month;
totalMonths = 12 - monthDifference;
}
if ((firstDate.Day - secondDate.Day) == 30)
{
totalMonths += 1;
if (totalMonths % 12 == 0)
{
totalYears += 1;
totalMonths = 0;
}
}
Maybe this will be helpful for answering the question: Count of days in given year,
new DateTime(anyDate.Year, 12, 31).DayOfYear //will include leap years too
Regarding DateTime.DayOfYear Property.
The following is based off Dana's simple code which produces the correct answer in most cases. But it did not take in to account less than a year between dates. So here is the code that I use to produce consistent results:
public static int DateDiffYears(DateTime startDate, DateTime endDate)
{
var yr = endDate.Year - startDate.Year - 1 +
(endDate.Month >= startDate.Month && endDate.Day >= startDate.Day ? 1 : 0);
return yr < 0 ? 0 : yr;
}
Related
I got here a scenario where I input an information but the code does does not work. What happen is when I input 12/11/2015, the Address2Panel shows. Which is wrong because there no more date that I can input because Person A is born in 12/11/2015. The logic should Enter addresses for the past 5 years. But it goes wrong if the Birthdate gap is not lesser the 5 years from the current date.
Person A Birthday = 12/11/2015
Person A StartLiving = 12/11/2015 because its the day he/she was born.
Should not display Address2Panel
int CurrentDateInMonths = (((DateTime.Today.Year) * 12) + (DateTime.Today.Month));
static int AlienMonthsAtCurrentAddress = 0;
DateTime myDateTime;
//LivedHere = 12/11/2015
myDateTime = DateTime.Parse(LivedHere.Text);
AlienMonthsAtCurrentAddress = (CurrentDateInMonths - (((Convert.ToInt16(myDateTime.Year)) * 12) + Convert.ToInt16(myDateTime.Month)));
if (AlienMonthsAtCurrentAddress < 60)
{
Address2Panel.Visible = true;//shows the Address2Panel
}
else
{
ClearAddress2Panel();//hides also the Address2Panel
}
Any suggestion how should I improve my formula and date time manipulation?
no need to convert date into months, subtract dates using DateTime.Subtract method :
From MSDN, DateTime.Subtract Method subtracts the specified date and time from this instance.It returns a TimeSpan object which has a property Days
static int AlienMonthsAtCurrentAddress = 0;
try
{
DateTime myDateTime;
myDateTime = DateTime.Parse(LivedHere.Text);
// If you don't wish to subtract from today's date use required date in place of DateTime.Now
TimeSpan span = DateTime.Now.Subtract ( myDateTime );
if (span.Days < 60)
{
Address2Panel.Visible = true;//shows the Address2Panel
}
else
{
ClearAddress2Panel();//hides also the Address2Panel
}
}
catch { }
You could check years, months and days with a separately logic, and then get them all together:
DateTime date = new DateTime(2015,11,12)
DateTime input = getDate()
int years = input.Year - date.Year - 1
years += If(input.Month > date.Month, 1, 0)
years += If(input.Month = date.Month AndAlso input.Day >= date.Day, 1, 0)
This will output the exact number of years between two days (truncating the resulting integer). You'll just have to compare it to 5, in your case
I would like to compare 2 dates to confirm that the number of years between is >= 18. For example, if my 2 dates are 03-12-2011 and 03-12-1983 then this should pass validation, however, if my 2 dates are 03-12-2011 and 03-12-1995 then this should fail validation.
Can anyone help me?
hope this is what you are looking for
public bool CheckDate(DateTime date1, DateTime date2)
{
return date1.AddYears(-18) < date2;
}
I re-jigged your question title & description to make it a bit more clear. From what I gathered from your original post you are looking for an Age Verification function. Here is what I would do:
function VerifyAge(DateTime dateOfBirth)
{
DateTime now = DateTime.Today;
int age = now.Year - dateOfBirth.Year;
if (now.Month < dateOfBirth.Month || (now.Month == dateOfBirth.Month && now.Day < dateOfBirth.Day))
age--;
return age >= 18;
}
Use TimeSpan structure.
TimeSpan span= dateSecond - dateFirst;
int days=span.Days;
//or
int years = (int) (span.Days / 365.25);
Check the TimeSpan structure:
http://msdn.microsoft.com/en-us/library/system.timespan.aspx
Use Timespan:
TimeSpan day = 03-12-2011 - 03-12-1983;
double year = day.TotalDays / 365.25;
if (year > 18)
{
}
Maybe instead of 03-12-2011 you should use DateTime.Now
Here's a method to check if the age is more than 18:
private bool IsMoreThan18(DateTime from, DateTime to)
{
int age = to.Year - from.Year;
if (from > to.AddYears(-age)) age--;
return age >= 18;
}
DateTime zeroTime = new DateTime(1, 1, 1);
DateTime a = new DateTime(2008, 1, 1);
DateTime b = new DateTime(2016, 1, 1);
TimeSpan span = b - a;
// because we start at year 1 for the Gregorian
// calendar, we must subtract a year here.
int years = (zeroTime + span).Year - 1;
Console.WriteLine("Years elapsed: " + years);
Refrence Link
Try this....
Using this you can get the exact no of years between two days. Only you need to do is divide the date difference by 365.25
TimeSpan span = DateTime.Parse(To_Date) - DateTime.Parse(From_Date);
int years = (int)(span.Days / 365.25);
Create two DateTime objects and substract them from eachother.
The result is a DateTime object aswel:
DateTime dt = new DateTime(2011, 12, 03);
DateTime dt2 = new DateTime(1983, 12, 03);
DateTime dt3 = dt - dt2;
Now you can check dt3.Year for the number of years between them
How can I get the date of next Tuesday?
In PHP, it's as simple as strtotime('next tuesday');.
How can I achieve something similar in .NET
As I've mentioned in the comments, there are various things you could mean by "next Tuesday", but this code gives you "the next Tuesday to occur, or today if it's already Tuesday":
DateTime today = DateTime.Today;
// The (... + 7) % 7 ensures we end up with a value in the range [0, 6]
int daysUntilTuesday = ((int) DayOfWeek.Tuesday - (int) today.DayOfWeek + 7) % 7;
DateTime nextTuesday = today.AddDays(daysUntilTuesday);
If you want to give "a week's time" if it's already Tuesday, you can use:
// This finds the next Monday (or today if it's Monday) and then adds a day... so the
// result is in the range [1-7]
int daysUntilTuesday = (((int) DayOfWeek.Monday - (int) today.DayOfWeek + 7) % 7) + 1;
... or you could use the original formula, but from tomorrow:
DateTime tomorrow = DateTime.Today.AddDays(1);
// The (... + 7) % 7 ensures we end up with a value in the range [0, 6]
int daysUntilTuesday = ((int) DayOfWeek.Tuesday - (int) tomorrow.DayOfWeek + 7) % 7;
DateTime nextTuesday = tomorrow.AddDays(daysUntilTuesday);
EDIT: Just to make this nice and versatile:
public static DateTime GetNextWeekday(DateTime start, DayOfWeek day)
{
// The (... + 7) % 7 ensures we end up with a value in the range [0, 6]
int daysToAdd = ((int) day - (int) start.DayOfWeek + 7) % 7;
return start.AddDays(daysToAdd);
}
So to get the value for "today or in the next 6 days":
DateTime nextTuesday = GetNextWeekday(DateTime.Today, DayOfWeek.Tuesday);
To get the value for "the next Tuesday excluding today":
DateTime nextTuesday = GetNextWeekday(DateTime.Today.AddDays(1), DayOfWeek.Tuesday);
This should do the trick:
static DateTime GetNextWeekday(DayOfWeek day)
{
DateTime result = DateTime.Now.AddDays(1);
while( result.DayOfWeek != day )
result = result.AddDays(1);
return result;
}
There are less verbose and more clever/elegant solutions to this problem, but the following C# function works really well for a number of situations.
/// <summary>
/// Find the closest weekday to the given date
/// </summary>
/// <param name="includeStartDate">if the supplied date is on the specified day of the week, return that date or continue to the next date</param>
/// <param name="searchForward">search forward or backward from the supplied date. if a null parameter is given, the closest weekday (ie in either direction) is returned</param>
public static DateTime ClosestWeekDay(this DateTime date, DayOfWeek weekday, bool includeStartDate = true, bool? searchForward=true)
{
if (!searchForward.HasValue && !includeStartDate)
{
throw new ArgumentException("if searching in both directions, start date must be a valid result");
}
var day = date.DayOfWeek;
int add = ((int)weekday - (int)day);
if (searchForward.HasValue)
{
if (add < 0 && searchForward.Value)
{
add += 7;
}
else if (add > 0 && !searchForward.Value)
{
add -= 7;
}
else if (add == 0 && !includeStartDate)
{
add = searchForward.Value ? 7 : -7;
}
}
else if (add < -3)
{
add += 7;
}
else if (add > 3)
{
add -= 7;
}
return date.AddDays(add);
}
#Jon Skeet good answer.
For previous Day:
private DateTime GetPrevWeekday(DateTime start, DayOfWeek day) {
// The (... - 7) % 7 ensures we end up with a value in the range [0, 6]
int daysToRemove = ((int) day - (int) start.DayOfWeek - 7) % 7;
return start.AddDays(daysToRemove);
}
Thanks!!
DateTime nextTuesday = DateTime.Today.AddDays(((int)DateTime.Today.DayOfWeek - (int)DayOfWeek.Tuesday) + 7);
Very simple sample to include or exclude current date, you specify the date and the day the week you are interested in.
public static class DateTimeExtensions
{
/// <summary>
/// Gets the next date.
/// </summary>
/// <param name="date">The date to inspected.</param>
/// <param name="dayOfWeek">The day of week you want to get.</param>
/// <param name="exclDate">if set to <c>true</c> the current date will be excluded and include next occurrence.</param>
/// <returns></returns>
public static DateTime GetNextDate(this DateTime date, DayOfWeek dayOfWeek, bool exclDate = true)
{
//note: first we need to check if the date wants to move back by date - Today, + diff might move it forward or backwards to Today
//eg: date - Today = 0 - 1 = -1, so have to move it forward
var diff = dayOfWeek - date.DayOfWeek;
var ddiff = date.Date.Subtract(DateTime.Today).Days + diff;
//note: ddiff < 0 : date calculates to past, so move forward, even if the date is really old, it will just move 7 days from date passed in
//note: ddiff >= (exclDate ? 6 : 7) && diff < 0 : date is into the future, so calculated future weekday, based on date
if (ddiff < 0 || ddiff >= (exclDate ? 6 : 7) && diff < 0)
diff += 7;
//note: now we can get safe values between 0 - 6, especially if past dates is being used
diff = diff % 7;
//note: if diff is 0 and we are excluding the date passed, we will add 7 days, eg: 1 week
diff += diff == 0 & exclDate ? 7 : 0;
return date.AddDays(diff);
}
}
some test cases
[TestMethod]
public void TestNextDate()
{
var date = new DateTime(2013, 7, 15);
var start = date;
//testing same month - forwardOnly
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Tuesday)); //16
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Wednesday)); //17
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Thursday)); //18
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Friday)); //19
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Saturday)); //20
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Sunday)); //21
Assert.AreEqual(start.AddDays(1), date.GetNextDate(DayOfWeek.Monday)); //22
//testing same month - include date
Assert.AreEqual(start = date, date.GetNextDate(DayOfWeek.Monday, false)); //15
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Tuesday, false)); //16
Assert.AreEqual(start.AddDays(1), date.GetNextDate(DayOfWeek.Wednesday, false)); //17
//testing month change - forwardOnly
date = new DateTime(2013, 7, 29);
start = date;
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Tuesday)); //30
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Wednesday)); //31
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Thursday)); //2013/09/01-month increased
Assert.AreEqual(start.AddDays(1), date.GetNextDate(DayOfWeek.Friday)); //02
//testing year change
date = new DateTime(2013, 12, 30);
start = date;
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Tuesday)); //31
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Wednesday)); //2014/01/01 - year increased
Assert.AreEqual(start = start.AddDays(1), date.GetNextDate(DayOfWeek.Thursday)); //02
}
DateTime nexttuesday=DateTime.Today.AddDays(1);
while(nexttuesday.DayOfWeek!=DayOfWeek.Tuesday)
nexttuesday = nexttuesday.AddDays(1);
Now in oneliner flavor - in case you need to pass it as parameter into some mechanism.
DateTime.Now.AddDays(((int)yourDate.DayOfWeek - (int)DateTime.Now.DayOfWeek + 7) % 7).Day
In this specific case:
DateTime.Now.AddDays(((int)DayOfWeek.Tuesday - (int)DateTime.Now.DayOfWeek + 7) % 7).Day
It could be an extension also, it all depends
public static class DateTimeExtensions
{
public static IEnumerable<DateTime> Next(this DateTime date, DayOfWeek day)
{
// This loop feels expensive and useless, but the point is IEnumerable
while(true)
{
if (date.DayOfWeek == day)
{
yield return date;
}
date = date.AddDays(1);
}
}
}
Usage
var today = DateTime.Today;
foreach(var monday in today.Next(DayOfWeek.Monday))
{
Console.WriteLine(monday);
Console.ReadKey();
}
I want to get next day from this time include today
also I want it to be at 12:00 AM
public static DateTime GetNextWeekday(DateTime start, DayOfWeek day , bool includetoday = false) {
if (includetoday && start.DayOfWeek == day) return start.Date;
int daysToAdd = ((int)day - (int)start.DayOfWeek + 7) % 7;
return start.Date.AddDays(daysToAdd);
}
Objective C Version:
+(NSInteger) daysUntilNextWeekday: (NSDate*)startDate withTargetWeekday: (NSInteger) targetWeekday
{
NSInteger startWeekday = [[NSCalendar currentCalendar] component:NSCalendarUnitWeekday fromDate:startDate];
return (targetWeekday - startWeekday + 7) % 7;
}
Example: given two dates below, finish is always greater than or equal to start
start = 2001 Jan 01
finish = 2002 Mar 15
So from 2001 Jan 01 to the end of 2002 Feb
months = 12 + 2 = 14
For 2002 March
15/30 = 0.5
so grand total is 14.5 months difference.
It's very easy to work out by hand but how do I code it elegantly? At the moment I have the combination of a lot of if else and while loops to achieve what I want but I believe there are simpler solutions out there.
Update: the output needs to be precise (not approximation) for example:
if start 2001 Jan 01 and finish 2001 Apr 16, the output should be 1 + 1 + 1= 3 (for Jan, Feb and Mar) and 16 / 31 = 0.516 month, so the total is 3.516.
Another example would be if I start on 2001 Jul 5 and finish on 2002 Jul 10, the output should be 11 month up to the end of June 2002, and (31-5)/31 = 0.839 and 10/31 = 0.323 months, so the total is 11 + 0.839 + 0.323 = 12.162.
I extended Josh Stodola's code and Hightechrider's code:
public static decimal GetMonthsInRange(this IDateRange thisDateRange)
{
var start = thisDateRange.Start;
var finish = thisDateRange.Finish;
var monthsApart = Math.Abs(12*(start.Year - finish.Year) + start.Month - finish.Month) - 1;
decimal daysInStartMonth = DateTime.DaysInMonth(start.Year, start.Month);
decimal daysInFinishMonth = DateTime.DaysInMonth(finish.Year, finish.Month);
var daysApartInStartMonth = (daysInStartMonth - start.Day + 1)/daysInStartMonth;
var daysApartInFinishMonth = finish.Day/daysInFinishMonth;
return monthsApart + daysApartInStartMonth + daysApartInFinishMonth;
}
I gave an int answer before, and then realized what you asked for a more precise answer. I was tired, so I deleted and went to bed. So much for that, I was unable to fall asleep! For some reason, this question really bugged me, and I had to solve it. So here you go...
static void Main(string[] args)
{
decimal diff;
diff = monthDifference(new DateTime(2001, 1, 1), new DateTime(2002, 3, 15));
Console.WriteLine(diff.ToString("n2")); //14.45
diff = monthDifference(new DateTime(2001, 1, 1), new DateTime(2001, 4, 16));
Console.WriteLine(diff.ToString("n2")); //3.50
diff = monthDifference(new DateTime(2001, 7, 5), new DateTime(2002, 7, 10));
Console.WriteLine(diff.ToString("n2")); //12.16
Console.Read();
}
static decimal monthDifference(DateTime d1, DateTime d2)
{
if (d1 > d2)
{
DateTime hold = d1;
d1 = d2;
d2 = hold;
}
int monthsApart = Math.Abs(12 * (d1.Year-d2.Year) + d1.Month - d2.Month) - 1;
decimal daysInMonth1 = DateTime.DaysInMonth(d1.Year, d1.Month);
decimal daysInMonth2 = DateTime.DaysInMonth(d2.Year, d2.Month);
decimal dayPercentage = ((daysInMonth1 - d1.Day) / daysInMonth1)
+ (d2.Day / daysInMonth2);
return monthsApart + dayPercentage;
}
Now I shall have sweet dreams. Goodnight :)
What you want is probably something close to this ... which pretty much follows your explanation as to how to calculate it:
var startofd1 = d1.AddDays(-d1.Day + 1);
var startOfNextMonthAfterd1 = startofd1.AddMonths(1); // back to start of month and then to next month
int daysInFirstMonth = (startOfNextMonthAfterd1 - startofd1).Days;
double fraction1 = (double)(daysInFirstMonth - (d1.Day - 1)) / daysInFirstMonth; // fractional part of first month remaining
var startofd2 = d2.AddDays(-d2.Day + 1);
var startOfNextMonthAfterd2 = startofd2.AddMonths(1); // back to start of month and then to next month
int daysInFinalMonth = (startOfNextMonthAfterd2 - startofd2).Days;
double fraction2 = (double)(d2.Day - 1) / daysInFinalMonth; // fractional part of last month
// now find whole months in between
int monthsInBetween = (startofd2.Year - startOfNextMonthAfterd1.Year) * 12 + (startofd2.Month - startOfNextMonthAfterd1.Month);
return monthsInBetween + fraction1 + fraction2;
NB This has not been tested very well but it shows how to handle problems like this by finding well known dates at the start of months around the problem values and then working off them.
While loops for date time calculations are always a bad idea: see http://www.zuneboards.com/forums/zune-news/38143-cause-zune-30-leapyear-problem-isolated.html
Depending on how exactly you want your logic to work, this would at least give you a decent approximation:
// 365 days per year + 1 day per leap year = 1461 days every 4 years
// But years divisible by 100 are not leap years
// So 1461 days every 4 years - 1 day per 100th year = 36524 days every 100 years
// 12 months per year = 1200 months every 100 years
const double DaysPerMonth = 36524.0 / 1200.0;
double GetMonthsDifference(DateTime start, DateTime finish)
{
double days = (finish - start).TotalDays;
return days / DaysPerMonth;
}
One way to do this is that you'll see around quite a bit is:
private static int monthDifference(DateTime startDate, DateTime endDate)
{
int monthsApart = 12 * (startDate.Year - endDate.Year) + startDate.Month - endDate.Month;
return Math.Abs(monthsApart);
}
However, you want "partial months" which this doesn't give. But what is the point in comparing apples (January/March/May/July/August/October/December) with oranges (April/June/September/November) or even bananas that are sometimes coconuts (February)?
An alternative is to import Microsoft.VisualBasic and do this:
DateTime FromDate;
DateTime ToDate;
FromDate = DateTime.Parse("2001 Jan 01");
ToDate = DateTime.Parse("2002 Mar 15");
string s = DateAndTime.DateDiff (DateInterval.Month, FromDate,ToDate, FirstDayOfWeek.System, FirstWeekOfYear.System ).ToString();
However again:
The return value for
DateInterval.Month is calculated
purely from the year and month parts
of the arguments
[Source]
Just improved Josh's answer
static decimal monthDifference(DateTime d1, DateTime d2)
{
if (d1 > d2)
{
DateTime hold = d1;
d1 = d2;
d2 = hold;
}
decimal monthsApart = Math.Abs((12 * (d1.Year - d2.Year)) + d2.Month - d1.Month - 1);
decimal daysinStartingMonth = DateTime.DaysInMonth(d1.Year, d1.Month);
monthsApart = monthsApart + (1-((d1.Day - 1) / daysinStartingMonth));
// Replace (d1.Day - 1) with d1.Day incase you DONT want to have both inclusive difference.
decimal daysinEndingMonth = DateTime.DaysInMonth(d2.Year, d2.Month);
monthsApart = monthsApart + (d2.Day / daysinEndingMonth);
return monthsApart;
}
The answer works perfectly and while the terseness of the code makes it very small I had to break everything apart into smaller functions with named variables so that I could really understand what was going on... So, basically I just took Josh Stodola's code and Hightechrider's mentioned in Jeff's comment and made it smaller with comments explaining what was going on and why the calculations were being made, and hopefully this may help someone else:
[Test]
public void Calculate_Total_Months_Difference_Between_Two_Dates()
{
var startDate = DateTime.Parse( "10/8/1996" );
var finishDate = DateTime.Parse( "9/8/2012" ); // this should be now:
int numberOfMonthsBetweenStartAndFinishYears = getNumberOfMonthsBetweenStartAndFinishYears( startDate, finishDate );
int absMonthsApartMinusOne = getAbsMonthsApartMinusOne( startDate, finishDate, numberOfMonthsBetweenStartAndFinishYears );
decimal daysLeftToCompleteStartMonthPercentage = getDaysLeftToCompleteInStartMonthPercentage( startDate );
decimal daysCompletedSoFarInFinishMonthPercentage = getDaysCompletedSoFarInFinishMonthPercentage( finishDate );
// .77 + .26 = 1.04
decimal totalDaysDifferenceInStartAndFinishMonthsPercentage = daysLeftToCompleteStartMonthPercentage + daysCompletedSoFarInFinishMonthPercentage;
// 13 + 1.04 = 14.04 months difference.
decimal totalMonthsDifference = absMonthsApartMinusOne + totalDaysDifferenceInStartAndFinishMonthsPercentage;
//return totalMonths;
}
private static int getNumberOfMonthsBetweenStartAndFinishYears( DateTime startDate, DateTime finishDate )
{
int yearsApart = startDate.Year - finishDate.Year;
const int INT_TotalMonthsInAYear = 12;
// 12 * -1 = -12
int numberOfMonthsBetweenYears = INT_TotalMonthsInAYear * yearsApart;
return numberOfMonthsBetweenYears;
}
private static int getAbsMonthsApartMinusOne( DateTime startDate, DateTime finishDate, int numberOfMonthsBetweenStartAndFinishYears )
{
// This may be negative i.e. 7 - 9 = -2
int numberOfMonthsBetweenStartAndFinishMonths = startDate.Month - finishDate.Month;
// Absolute Value Of Total Months In Years Plus The Simple Months Difference Which May Be Negative So We Use Abs Function
int absDiffInMonths = Math.Abs( numberOfMonthsBetweenStartAndFinishYears + numberOfMonthsBetweenStartAndFinishMonths );
// Subtract one here because we are going to use a perecentage difference based on the number of days left in the start month
// and adding together the number of days that we've made it so far in the finish month.
int absMonthsApartMinusOne = absDiffInMonths - 1;
return absMonthsApartMinusOne;
}
/// <summary>
/// For example for 7/8/2012 there are 24 days left in the month so about .77 percentage of month is left.
/// </summary>
private static decimal getDaysLeftToCompleteInStartMonthPercentage( DateTime startDate )
{
// startDate = "7/8/2012"
// 31
decimal daysInStartMonth = DateTime.DaysInMonth( startDate.Year, startDate.Month );
// 31 - 8 = 23
decimal totalDaysInStartMonthMinusStartDay = daysInStartMonth - startDate.Day;
// add one to mark the day as being completed. 23 + 1 = 24
decimal daysLeftInStartMonth = totalDaysInStartMonthMinusStartDay + 1;
// 24 / 31 = .77 days left to go in the month
decimal daysLeftToCompleteInStartMonthPercentage = daysLeftInStartMonth / daysInStartMonth;
return daysLeftToCompleteInStartMonthPercentage;
}
/// <summary>
/// For example if the finish date were 9/8/2012 we've completed 8 days so far or .24 percent of the month
/// </summary>
private static decimal getDaysCompletedSoFarInFinishMonthPercentage( DateTime finishDate )
{
// for septebmer = 30 days in month.
decimal daysInFinishMonth = DateTime.DaysInMonth( finishDate.Year, finishDate.Month );
// 8 days divided by 30 = .26 days completed so far in finish month.
decimal daysCompletedSoFarInFinishMonthPercentage = finishDate.Day / daysInFinishMonth;
return daysCompletedSoFarInFinishMonthPercentage;
}
This solution calculates whole months and then adds the partial month based on the end of the time period. This way it always calculates full months between the dates' day-of-month and then calculates the partial month based on the number of remaining days.
public decimal getMonthDiff(DateTime date1, DateTime date2) {
// Make parameters agnostic
var earlyDate = (date1 < date2 ? date1 : date2);
var laterDate = (date1 > date2 ? date1 : date2);
// Calculate the change in full months
decimal months = ((laterDate.Year - earlyDate.Year) * 12) + (laterDate.Month - earlyDate.Month) - 1;
// Add partial months based on the later date
if (earlyDate.Day <= laterDate.Day) {
decimal laterMonthDays = DateTime.DaysInMonth(laterDate.Year, laterDate.Month);
decimal laterPartialMonth = ((laterDate.Day - earlyDate.Day) / laterMonthDays);
months += laterPartialMonth + 1;
} else {
var laterLastMonth = laterDate.AddMonths(-1);
decimal laterLastMonthDays = DateTime.DaysInMonth(laterLastMonth.Year, laterLastMonth.Month);
decimal laterPartialMonth = ((laterLastMonthDays - earlyDate.Day + laterDate.Day) / laterLastMonthDays);
months += laterPartialMonth;
}
return months;
}
The calculation below is one that is according the way the Dutch Tax Authority wants months calculated. This means that when the starts day is for example feb 22, march 23 should be result in something above 1 and not just something like 0.98.
private decimal GetMonthDiffBetter(DateTime date1, DateTime date2)
{
DateTime start = date1 < date2 ? date1 : date2;
DateTime end = date1 < date2 ? date2 : date1;
int totalYearMonths = (end.Year - start.Year) * 12;
int restMonths = end.Month - start.Month;
int totalMonths = totalYearMonths + restMonths;
decimal monthPart = (decimal)end.Day / (decimal)start.Day;
return totalMonths - 1 + monthPart;
}`
This should get you where you need to go:
DateTime start = new DateTime(2001, 1, 1);
DateTime finish = new DateTime(2002, 3, 15);
double diff = (finish - start).TotalDays / 30;
the framework as a TimeSpan object that is a result of subtracting two dates.
the subtraction is already considering the various option of February(28/29 days a month) so in my opinion this is the best practice
after you got it you can format it the way you like best
DateTime dates1 = new DateTime(2010, 1, 1);
DateTime dates2 = new DateTime(2010, 3, 15);
var span = dates1.Subtract(dates2);
span.ToString("your format here");
private Double GetTotalMonths(DateTime future, DateTime past)
{
Double totalMonths = 0.0;
while ((future - past).TotalDays > 28 )
{
past = past.AddMonths(1);
totalMonths += 1;
}
var daysInCurrent = DateTime.DaysInMonth(future.Year, future.Month);
var remaining = future.Day - past.Day;
totalMonths += ((Double)remaining / (Double)daysInCurrent);
return totalMonths;
}
For the purposes of this question, let's assume the user will be from the US and will use the standard Gregorian calendar. So, a calendar week starts on Sunday and ends on Saturday.
What I'm trying to do is determine the number of calendar weeks that exist between two dates. A perfect example of my problem exists in October 2010. Between 10/16 and 10/31 there are 4 calendar weeks.
October 10 - October 16
October 17 - October 23
October 24 - October 30
October 31 - November 6
I'd prefer to stay away from any hardcoded logic like:
if (Day == DayOfWeek.Saturday && LastDayOfMonth == 31) { ... }
Can anyone think of a logical way to do this?
UPDATE:
Thanks for all the great responses, after some consideration here is the solution I used:
//get the start and end dates of the current pay period
DateTime currentPeriodStart = SelectedPeriod.Model.PeriodStart;
DateTime currentPeriodEnd = SelectedPeriod.Model.PeriodEnd;
//get the first sunday & last saturday span that encapsulates the current pay period
DateTime firstSunday = DayExtensions.SundayBeforePeriodStart(currentPeriodStart);
DateTime lastSaturday = DayExtensions.SaturdayAfterPeriodEnd(currentPeriodEnd);
//get the number of calendar weeks in the span
int numberOfCalendarWeeks = DayExtensions.CalendarWeeks(firstSunday, lastSaturday);
And here are the methods from the helper class:
/// <summary>
/// Get the first Sunday before the pay period start date
/// </summary>
/// <param name="periodStartDate">Date of the pay period start date</param>
/// <returns></returns>
public static DateTime SundayBeforePeriodStart(DateTime periodStartDate)
{
DateTime firstDayOfWeekBeforeStartDate;
int daysBetweenStartDateAndPreviousFirstDayOfWeek = (int)periodStartDate.DayOfWeek - (int)DayOfWeek.Sunday;
if (daysBetweenStartDateAndPreviousFirstDayOfWeek >= 0)
{
firstDayOfWeekBeforeStartDate = periodStartDate.AddDays(-daysBetweenStartDateAndPreviousFirstDayOfWeek);
}
else
{
firstDayOfWeekBeforeStartDate = periodStartDate.AddDays(-(daysBetweenStartDateAndPreviousFirstDayOfWeek + 7));
}
return firstDayOfWeekBeforeStartDate;
}
/// <summary>
/// Get the first Saturday after the period end date
/// </summary>
/// <param name="periodEndDate">Date of the pay period end date</param>
/// <returns></returns>
public static DateTime SaturdayAfterPeriodEnd(DateTime periodEndDate)
{
DateTime lastDayOfWeekAfterEndDate;
int daysBetweenEndDateAndFollowingLastDayOfWeek = (int)DayOfWeek.Saturday - (int)periodEndDate.DayOfWeek;
if (daysBetweenEndDateAndFollowingLastDayOfWeek >= 0)
{
lastDayOfWeekAfterEndDate = periodEndDate.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek);
}
else
{
lastDayOfWeekAfterEndDate = periodEndDate.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek + 7);
}
return lastDayOfWeekAfterEndDate;
}
/// <summary>
/// Get the calendar weeks between 2 dates
/// </summary>
/// <param name="d1">First day of date span</param>
/// <param name="d2">Last day of date span</param>
/// <returns></returns>
public static int CalendarWeeks(DateTime d1, DateTime d2)
{
return 1 + (int)((d2 - d1).TotalDays / 7);
}
And if you're curious, this is what I end up doing with the dates:
//create an array of all the sundays in this span
DateTime[] _sundays = new DateTime[numberOfCalendarWeeks];
//put the first sunday in the period
_sundays[0] = firstSunday;
//step through each week and get each sunday until you reach the last saturday
for (int i = 1; i <= numberOfCalendarWeeks - 1; i++)
{
DateTime d = new DateTime();
d = firstSunday.AddDays(i * 7);
_sundays[i] = d;
}
for (int i = 0; i <= _sundays.Length-1; i++)
{
//bind my view model with each sunday.
}
Here's a general solution which I believe should work for any choice of week starting and ending days. You could simplify it for your case, but this code gives you the option of changing the week's start and end (e.g. to Monday to Sunday) if it becomes necessary. It's not uncommon in payroll applications for the definition of a calendar week to change.
DateTime periodStart = new DateTime(2010, 10, 17);
DateTime periodEnd = new DateTime(2010, 11, 14);
const DayOfWeek FIRST_DAY_OF_WEEK = DayOfWeek.Monday;
const DayOfWeek LAST_DAY_OF_WEEK = DayOfWeek.Sunday;
const int DAYS_IN_WEEK = 7;
DateTime firstDayOfWeekBeforeStartDate;
int daysBetweenStartDateAndPreviousFirstDayOfWeek = (int)periodStart.DayOfWeek - (int)FIRST_DAY_OF_WEEK;
if (daysBetweenStartDateAndPreviousFirstDayOfWeek >= 0)
{
firstDayOfWeekBeforeStartDate = periodStart.AddDays(-daysBetweenStartDateAndPreviousFirstDayOfWeek);
}
else
{
firstDayOfWeekBeforeStartDate = periodStart.AddDays(-(daysBetweenStartDateAndPreviousFirstDayOfWeek + DAYS_IN_WEEK));
}
DateTime lastDayOfWeekAfterEndDate;
int daysBetweenEndDateAndFollowingLastDayOfWeek = (int)LAST_DAY_OF_WEEK - (int)periodEnd.DayOfWeek;
if (daysBetweenEndDateAndFollowingLastDayOfWeek >= 0)
{
lastDayOfWeekAfterEndDate = periodEnd.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek);
}
else
{
lastDayOfWeekAfterEndDate = periodEnd.AddDays(daysBetweenEndDateAndFollowingLastDayOfWeek + DAYS_IN_WEEK);
}
int calendarWeeks = 1 + (int)((lastDayOfWeekAfterEndDate - firstDayOfWeekBeforeStartDate).TotalDays / DAYS_IN_WEEK);
The way I would tackle this is to get the beginning of the week for any given date. Using that, you would subtract the result of the start date from the result of the end date. Your day difference would then always be a multiple of 7, so divide and add 1 (0 days => 1 week, 7 days => 2 weeks, etc.). This would tell you how many calendar weeks were covered or represented by any two dates.
static int GetWeeksCovered(DateTime startDate, DateTime endDate)
{
if (endDate < startDate)
throw new ArgumentException("endDate cannot be less than startDate");
return (GetBeginningOfWeek(endDate).Subtract(GetBeginningOfWeek(startDate)).Days / 7) + 1;
}
static DateTime GetBeginningOfWeek(DateTime date)
{
return date.AddDays(-1 * (int)date.DayOfWeek).Date;
}
16-Oct-2010 and 16-Oct-2010 => 1 week covered (or represented).
16-Oct-2010 and 31-Oct-2010 => 4 weeks covered, as per the spec.
Bear in mind, that week calculations are done differently in different cultures and there is not a bug if you see week number 53!
using System.Globalization;
CultureInfo cultInfo = CultureInfo.CurrentCulture;
int weekNumNow = cultInfo.Calendar.GetWeekOfYear(DateTime.Now,
cultInfo.DateTimeFormat.CalendarWeekRule,
cultInfo.DateTimeFormat.FirstDayOfWeek);
private static int weekDifference(DateTime startDate, DateTime endDate)
{
int monthsApart = 12 * (startDate.Year - endDate.Year) + startDate.Month - endDate.Month;
return Math.Abs(monthsApart*4);
}
Cant See a better way right off the bat.
Saturday is the last day of the week huh?
public int CalendarWeeks(DateTime from, DateTime to) {
// number of multiples of 7
// (rounded up, since 15 days would span at least 3 weeks)
// and if we end on a day before we start, we know it's another week
return (int)Math.Ceiling(to.Subtract(from).Days / 7.0) +
(to.DayOfWeek <= from.DayOfWeek) ? 1 : 0;
}
The following seems to work for any date range. It should be culturally sound, and should account for leap years/days or other calendar oddities:
private static int getWeeksSpannedBy(DateTime first, DateTime last)
{
var calendar = CultureInfo.CurrentCulture.Calendar;
var weekRule = CultureInfo.CurrentCulture.DateTimeFormat.CalendarWeekRule;
var firstDayOfWeek = DayOfWeek.Sunday;
int lastWeek = calendar.GetWeekOfYear(last, weekRule, firstDayOfWeek);
int firstWeek = calendar.GetWeekOfYear(first, weekRule, firstDayOfWeek);
int weekDiff = lastWeek - firstWeek + 1;
return weekDiff;
}
static void Main(string[] args)
{
int weeks1 = getWeeksSpannedBy(new DateTime(2010, 1, 3), new DateTime(2010, 1, 9));
int weeks2 = getWeeksSpannedBy(new DateTime(2010, 10, 16), new DateTime(2010, 10, 31));
int weeks3 = getWeeksSpannedBy(new DateTime(2008, 2, 1), new DateTime(2008, 2, 29));
int weeks4 = getWeeksSpannedBy(new DateTime(2012, 2, 1), new DateTime(2012, 2, 29));
Console.WriteLine("Weeks Difference #1: " + weeks1);
Console.WriteLine("Weeks Difference #2: " + weeks2);
Console.WriteLine("Weeks Difference #3: " + weeks3);
Console.WriteLine("Weeks Difference #4: " + weeks4);
Console.ReadLine();
}
Prints out the following, which is correct for all date ranges, past, present, or future (leap year 2008 and 2012 both have 5 weeks between Feb 1 and Feb 29):
Weeks Difference #1: 1
Weeks Difference #2: 4
Weeks Difference #3: 5
Weeks Difference #4: 5
private static int weekDifference(DateTime startDate, DateTime endDate)
{
const int firstDayOfWeek = 0; // Sunday
int wasteDaysStart = (7+startDate.DatOfWeek-firstDayOfWeek)%7;
return (int)(((endDate-startDate).TotalDays() + wasteDaysStart + 6)/7);
}
Warning: untested code. Please test and remove note.