I was looking for a way to fetch the same day of the current week as a year ago. For example, today is:
August 10th 2022 - Wednesday.
Assume this is the check-in date, the check-out date I expect to get is:
August 11, 2021 - Wednesday.
Because it's the same day (Wednesday) as last year. But I need to take leap years into account, so I need to see if the current year is a leap year and if it is, if it has passed the 29th of February, the same with the date last year.
How to do this using .net core ? I thought of something like:
private DateTime GetDayOneYearBefore()
{
if(DateTime.IsLeapYear(DateTime.Today.Year) && DateTime.Today.Month > 2){
return DateTime.Today.AddDays(-365);
}
else if(DateTime.IsLeapYear(DateTime.Today.Year) && DateTime.Today.Month <= 2){
return DateTime.Today.AddDays(-364);
}
}
Since you mention the "same week" I suppose you want to get the same day of the week in the same week number?
If so, you can do the following:
// In the System.DayOfWeek enum Sunday = 0, while Monday = 1
// This converts DateTime.DayOfWeek to a range where Monday = 0 and Sunday = 6
static int DayOfWeek(DateTime dt)
{
const int weekStart = (int)System.DayOfWeek.Monday;
const int daysInAWeek = 7;
return (daysInAWeek - (weekStart - (int)dt.DayOfWeek)) % daysInAWeek;
}
var calendar = CultureInfo.CurrentCulture.Calendar;
var weekNum = calendar.GetWeekOfYear(DateTime.Today, CalendarWeekRule.FirstFourDayWeek, System.DayOfWeek.Monday);
var todayLastYear = DateTime.Today.AddYears(-1);
var lastYearWeekNum = calendar.GetWeekOfYear(todayLastYear, CalendarWeekRule.FirstFourDayWeek, System.DayOfWeek.Monday);
var sameWeekLastYear = todayLastYear.AddDays(7 * (weekNum - lastYearWeekNum));
var sameDaySameWeekLastYear = sameWeekLastYear.AddDays(DayOfWeek(DateTime.Today) - DayOfWeek(sameWeekLastYear));
As you might notice there's a little convertion method, since I normally work with Monday being the first day of the week. If you prefer a different day to be the first day of the week, simply replace System.DayOfWeek.Monday with which ever day you'd like.
See this fiddle for a test run.
I've been trying to figure out how to take next available day based on Present day i.e., if today is Friday, then search in Array for the next nearest day like if Array values are 1[Monday], 2[Tuesday], 4[Thursday], 6[Saturday] then my next day should be Saturday.
Here is what i tried
//Here i'll get days like 0, 2, 3, 4, 6 pattern, and i'm spliting them based on comma to get single-single day value in array of string
string[] GetDays = DayInWeek.Split(','); [Here day patterns will change everytime, based on user selection]
//Here i'm looping to take each day and get Enum Text based on Enum Value
foreach (string FirstDay in GetDays)
{
//Here i'm converting the string value into int and passing to DayOfWeek Enum to get respective day
DayOfWeek DayChoosen = ((DayOfWeek)(Convert.ToInt32(FirstDay)));
//Here i have my actual day for example Friday
DayOfWeek StartDay = "Friday";
//Here i need condition to find next available day in the foreach i.e., after Friday next value should be Saturday, or Sunday, Monday & so on until Friday==Friday
if (StartDay == DayChoosen)
{
//End foreach
}
}
As i told based on present Day i should find next available day i.e, if Friday i should search for Saturday, if Saturday is not there then Sunday, Monday and so on till Friday=Friday
You don't need all these manipulations with foreach.
You can do the following:
private int nextDay(string dayInWeek, int startDay)
{
int[] getDays = dayInWeek.Split(',').Select(int.Parse).ToArray();
return getDays.Where(d => d > startDay).Any()
? getDays.Where(d => d > startDay).Min()
: getDays.Min();
}
This algorithm checks if there are any days of a week, which are presented in your array, and come after the startDay. Else, it outputs the first available day in a week.
For example, for a string "0, 2, 3, 4, 6":
for startDay 0 - output 2, as it is the minimal integer which is more than 0
for startDay 1 - outputs 2
for startDay 3 - output 4
for startDay 6 it finds no items, which are more than 6, and outputs minimum 0
For string "5" (Friday only):
for startDay 5, 6 - finds no items which are more than 5, output minimum (5)
for startDay 0-4 - outputs 5, as the minimum number which is greater than 0-4
Try this;
//Here i'll get days like 0, 2, 3, 4, 6 pattern, and i'm splitting them based on comma to get single-single day value in array of string
string DayInWeek = "0, 2, 3, 4, 6";
string[] GetDays = DayInWeek.Split(','); //[Here day patterns will change everytime, based on user selection]
DayOfWeek nextAvailableDay;
//Here i'm looping to take each day and get Enum Text based on Enum Value
foreach (string FirstDay in GetDays)
{
//Here i'm converting the string value into int and passing to DayOfWeek Enum to get respective day
DayOfWeek DayChoosen = ((DayOfWeek)(Convert.ToInt32(FirstDay)));
//Here i have my actual day for example Friday
DayOfWeek StartDay = DayOfWeek.Friday;
//Here i need condition to find next available day in the foreach i.e., after Friday next value should be Saturday, or Sunday, Monday & so on until Friday==Friday
if (StartDay.Equals(DayChoosen))
break;
if (StartDay < DayChoosen)
{
nextAvailableDay = DayChoosen;
break;
}
continue;
}
You should play on int list. I will provide you the pseudo code.
Algorithm:
sort the available list
get all greater numbers (greater than your current one) from the list
select the minimum now, and break
if you don't have any greater number, select all the minimum numbers (less than your current one)
select maximum from this list now, and break
if you don't have any greater or less numbers, than select the same number and break
now convert the number into week day
It is the possible algorithm I came up to solve this problem. You can convert it into code. May be its not the best one but I am sure it will work fine.
check this:
Console.WriteLine("Kindly provide input");
string DayInWeek = Console.ReadLine();
string[] GetDays = DayInWeek.Split(',');
Array.Sort(GetDays);
DateTime dt = DateTime.Today;
int i = (int)dt.DayOfWeek;
Console.WriteLine("Today is " + (DayOfWeek)i);
bool flag = false;
foreach (string FirstDay in GetDays)
{
if (Convert.ToInt32(FirstDay) > i)
{
Console.WriteLine((DayOfWeek)Convert.ToInt32(FirstDay) + " is the next day");
flag = true;
break;
}
}
if (!flag)
{
Console.WriteLine((DayOfWeek)Convert.ToInt32(GetDays[0]) + " is the next day");
}
Console.ReadKey();
user just enter the day of week. For instance user enter friday. I need to find the exact date of given day and format will be like dd.MM.yyyy.
But I don't know how I do it.
Example:
label1 - Friday (entered by user)
label2 - 08.06.2012 (found by system)
label1 is just a string (just Friday). It's coming from webservice as a string variable. I need to find the date and compare with today, If it's not equal or small than today I give date of upcoming Friday, else I give the date of the Friday the week after.
"If it's not equal or small than today I give exact date, else I give next week date. "
Assuming that means that you return always the next date in future with the given day of week, the only exception is when today is the given day of week.
public static DateTime getNextWeekDaysDate(String englWeekDate)
{
var desired = (DayOfWeek)Enum.Parse(typeof(DayOfWeek), englWeekDate);
var current = DateTime.Today.DayOfWeek;
int c = (int)current;
int d = (int)desired;
int n = (7 - c + d);
return DateTime.Today.AddDays((n >= 7) ? n % 7 : n);
}
Let's test:
DateTime Monday = getNextWeekDaysDate("Monday"); // 2012-06-11
DateTime Tuesday = getNextWeekDaysDate("Tuesday"); // 2012-06-05 <-- !!! today
DateTime Wednesday= getNextWeekDaysDate("Wednesday"); // 2012-06-06
DateTime Thursday = getNextWeekDaysDate("Thursday"); // 2012-06-07
DateTime Friday = getNextWeekDaysDate("Friday"); // 2012-06-08
Create enum of days (i.e. monday - 0, tuesday - 1, etc);
Get DateTime.Now DayOfWeek and cast in some way it to your enum value.
Calculate difference between Now.DayOfWeek and user's day of the week;
Use DateTime.AddDays(difference).DayofTheWeek;
get current time with DateTime.now
Current day is DateTime.Now.DayOfWeek
Then get the day of week your user entered
Then your result is DateTime.now.AddDays( NowDayOfWeek - UserDayOfWeek).
This is a question of best practices. I have a utility that takes in a two digit year as a string and I need to convert it to a four digit year as a string. right now I do
//DOB's format is "MMM (D)D YY" that first digit of the day is not there for numbers 1-9
string tmpYear = rowIn.DOB.Substring(rowIn.DOB.Length - 3, 2); //-3 because it is 0 indexed
if (Convert.ToInt16(tmpYear) > 50)
tmpYear = String.Format("19{0}", tmpYear);
else
tmpYear = String.Format("20{0}", tmpYear);
I am sure I am doing it horribly wrong, any pointers?
The .NET framework has a method that does exactly what you want:
int fourDigitYear = CultureInfo.CurrentCulture.Calendar.ToFourDigitYear(twoDigitYear)
That way you will correctly adhere to current regional settings as defined in Control Panel (or group policy):
Given that there are people alive now born before 1950, but none born after 2010, your use of 50 as the flipping point seems broken.
For date of birth, can you not set the flip point to the 'year of now' (i.e. 10) in your app? Even then you'll have problems with those born before 1911...
There's no perfect way to do this - you're creating information out of thin air.
I've assumed DOB = date-of-birth. For other data (say, maturity of a financial instrument) the choice might be different, but just as imperfect.
You can also use the DateTime.TryParse method to convert your date. It uses the current culture settings to define the pivot year (in my case it is 2029)
DateTime resultDate;
Console.WriteLine("CultureInfo.CurrentCulture.Calendar.TwoDigitYearMax : {0}", System.Globalization.CultureInfo.CurrentCulture.Calendar.TwoDigitYearMax);
DateTime.TryParse("01/01/28", out resultDate);
Console.WriteLine("Generated date with year=28 - {0}",resultDate);
DateTime.TryParse("01/02/29",out resultDate);
Console.WriteLine("Generated date with year=29 - {0}", resultDate);
DateTime.TryParse("01/03/30", out resultDate);
Console.WriteLine("Generated date with year=30 - {0}", resultDate);
The output is:
CultureInfo.CurrentCulture.Calendar.TwoDigitYearMax : 2029
Generated date with year=28 - 01/01/2028 00:00:00
Generated date with year=29 - 01/02/2029 00:00:00
Generated date with year=30 - 01/03/1930 00:00:00
If you want to change the behavior you can create a culture with the year you want to use as pivot. This thread shows an example
DateTime.TryParse century control C#
But as martin stated, if you want to manage a time period that spans more than 100 year, there is no way to do it with only 2 digits.
I think Java has a good implementation of this:
http://java.sun.com/javase/6/docs/api/java/text/SimpleDateFormat.html#year
People rarely specify years far into the future using a two-digit code. The Java implementation handles this by assuming a range of 80 years behind and 20 years ahead of the current year. So right now, 30 would be 2030, while 31 would be 1931. Additionally, this implementation is flexible, modifying its ranges as time goes on, so that you don't have to change the code every decade or so.
I just tested, and Excel also uses these same rules for 2-digit year conversion. 1/1/29 turns into 1/1/2029. 1/1/30 turns into 1/1/1930.
The implementation of
System.Globalization.CultureInfo.CurrentCulture.Calendar.ToFourDigitYear
is
public virtual int ToFourDigitYear(int year)
{
if (year < 0)
throw new ArgumentOutOfRangeException("year", Environment.GetResourceString("ArgumentOutOfRange_NeedNonNegNum"));
if (year < 100)
return (this.TwoDigitYearMax / 100 - (year > this.TwoDigitYearMax % 100 ? 1 : 0)) * 100 + year;
else
return year;
}
Hope this helps!
It might be smarter to check tmpYear > currentYear%100. If it is, then it's 19XX, otherwise 20XX.
This solution we use for Expiration Dates, the user enters MM and YY into separate fields. This results in dates being the 31st or 30th and 28th or 29th also for February.
/// <summary>
/// Creates datetime for current century and sets days to end of month
/// </summary>
/// <param name="MM"></param>
/// <param name="YY"></param>
/// <returns></returns>
public static DateTime GetEndOfMonth(string MM, string YY)
{
// YY -> YYYY #RipVanWinkle
// Gets Current century and adds YY to it.
// Minus 5 to allow dates that may be expired to be entered.
// eg. today is 2017, 12 = 2012 and 11 = 2111
int currentYear = DateTime.Now.Year;
string thisYear = currentYear.ToString().Substring(0, 2) + YY;
int month = Int32.Parse(MM);
int year = Int32.Parse(thisYear);
if ((currentYear - 5) > year)
year += 100;
return new DateTime(year, month, DateTime.DaysInMonth(year, month));
}
This Method can convert the credit card last two year digits to four year
private static int ToFourDigitYear(int year)
{
string stringYear = year.ToString("00");
if (stringYear.Length == 2)
{
int currentYear = DateTime.Now.Year;
string firstTwoDigitsOfCurrentYear = currentYear.ToString().Substring(0, 2);
year = Convert.ToInt32(firstTwoDigitsOfCurrentYear + stringYear);
if (year < currentYear)
year = year + 100;
}
return year;
}
Out of curiosity, from where do you get this data? From a form? In that case; I would simply ask the user to fill in (or somehow select) the year with four digits or get the users age and month/day of birth, and use that data to figure out what year they were born. That way, you wouldn't have to worry about this problem at all :)
Edit: Use DateTime for working with this kind of data.
Try this simple code
//Invoke TextBoxDateFormat method with date as parameter.
Method
public void TextBoxDateFormat(string str1)
{
// Takes the current date format if MM/DD/YY or MM/DD/YYYY
DateTime dt = Convert.ToDateTime(str1);
//Converts the requested date into MM/DD/YYYY and assign it to textbox field
TextBox = String.Format("{0:MM/dd/yyyy}", dt.ToShortDateString());
//include your validation code if required
}
Had a similar issue, and came up with this... HTH!
value = this.GetDate()
if (value.Length >= 6)//ensure that the date is mmddyy
{
int year = 0;
if (int.TryParse(value.Substring(4, 2), out year))
{
int pastMillenium = int.Parse(DateTime.Now.ToString("yyyy").Substring(0, 2)) - 1;
if (year > int.Parse(DateTime.Now.ToString("yy")))//if its a future year it's most likely 19XX
{
value = string.Format("{0}{1}{2}", value.Substring(0, 4), pastMillenium, year.ToString().PadLeft(2, '0'));
}
else
{
value = string.Format("{0}{1}{2}", value.Substring(0, 4), pastMillenium + 1, year.ToString().PadLeft(2, '0'));
}
}
else
{
value = string.Empty;
}
}
else
{
value = string.Empty;
}
My answer will not match your question but for credit cards I just add 2 digits of current year
private int UpconvertTwoDigitYearToFour(int yearTwoOrFour)
{
try
{
if (yearTwoOrFour.ToString().Length <= 2)
{
DateTime yearOnly = DateTime.ParseExact(yearTwoOrFour.ToString("D2"), "yy", null);
return yearOnly.Year;
}
}
catch
{
}
return yearTwoOrFour;
}
If you calculate for a person he will probably not be more than 100 years...
Eg: 751212
var nr = "751212";
var century = DateTime.Now.AddYears(-100).Year.ToString().Substring(0, 2);
var days = (DateTime.Now - DateTime.Parse(century + nr)).Days;
decimal years = days / 365.25m;
if(years>=99)
century = DateTime.Now.Year.ToString().Substring(0, 2);
var fullnr = century+nr;
To change a 2-digit year to 4-digit current or earlier -
year = year + (DateTime.Today.Year - DateTime.Today.Year%100);
if (year > DateTime.Today.Year)
year = year - 100;
My two cents,
Given an age range=[18, 100+], two digits year=90, I can do
current year - twoDigitsYear = 2018 - 90 = 1928, I got 19, 28
hence 19 is the first two digits of year of born, and 28 is the age, which is
year=1990, age=28
But it won't work when age 0 and 100 both included in the range, same to some of the other answers here.
Based on above solutions, here is mine, i used in android while using java
it takes current year in two digit format then checks for if input
year length is equal to 2, if yes then it get current year and from
this year it splits first two digits of century, then it adds this
century with year user input. to make it 4 digit year.
public static int getConvertedYearFromTwoToFourDigits(String year) {
if (year.length() == 2) {
int currentYear = Calendar.getInstance().get(Calendar.YEAR);
String firstTwoDigitsOfCurrentYear = String.valueOf(currentYear).substring(0, 2);
year = firstTwoDigitsOfCurrentYear + year;
}
return Integer.parseInt(year);
}
int fYear = Convert.ToInt32(txtYear.Value.ToString().Substring(2, 2));
My answer will not match your question but for credit cards I just add 2 digits of current year
private int UpconvertTwoDigitYearToFour(int yearTwoOrFour)
{
try
{
if (yearTwoOrFour.ToString().Length <= 2)
{
DateTime yearOnly = DateTime.ParseExact(yearTwoOrFour.ToString("D2"), "yy", null);
return yearOnly.Year;
}
}
catch
{
}
return yearTwoOrFour;
}
How can i learn next wednesday, monday in a week? Forexample Today 06.02.2009 next Monday 09.02.2009 or wednesday 11.02.2009 there is any algorithm?
i need :
which day monday in comingweek?
findDay("Monday")
it must return 09.02.2009
=====================================================
findDay("Tuesday")
it must return 10.02.2009
public static DateTime GetNextDayDate(DayOfWeek day) {
DateTime now = DateTime.Now;
int dayDiff = (int)(now.DayOfWeek - day);
if (dayDiff <= 0) dayDiff += 7;
return now.AddDays(dayDiff);
}
DateTime now = DateTime.Now;
DateTime nextMonday = now.AddDays((int)now.DayOfWeek - (int)DayOfWeek.Monday);
Hum it seems that I answered too quickly. Actually there are more checking to do. Have a look at nobugz or peterchen answers.
I found a simpler solution:
DayOfWeek is an enum, as: Monday=1, Tuesday=2, etc.
So, to get next Monday (from today) you should use:
DateTime.Today.AddDays(8-(int)DateTime.Today.DayOfWeek)
where "8" is next week's Monday(according to the enum-> 1+7).
Replace the 8 for a 10 (i.e. Wednesday, 3+7) and you'll get next week's Wednesday, and so on...
Like Tyalis, but some extra checking is required:
int daysUntilMonday = ((int)DayOfWeek.Monday - (int)today.DayOfWeek;
if (daysUntilMonday <= 0)
daysUntilMonday += 7;
Monday = DateTime.Now.AddDays(daysUntilMonday);
Just iterate a bit:
DateTime baseDate = ...;
DayOfWeek requiredDayOfWeek = ...;
while(baseDate.DayOfWeek != requiredDayOfWeek)
baseDate = baseDate.AddDays(1);
You can also write an extension method if those are available:
static Next(this DateTime date, DayOfWeek requiredDayOfWeek) { ... }
and you'll get pretty syntax: today.Next(DayOfWeek.Saturday).