[Solved] I want to covert julian date(YYJJJ format) to any normal date format(MMDDYY) using c#. Is there any defined function for that?

Question

First of all, there is no YY, JJJ and DD formats as a custom date and time format. One solution might be to split your string Year and DayOfYear part and create a DateTime with JulianCalendar class.

string s = "05365";
int year = Convert.ToInt32(s.Substring(0, 2));
// Get year part from your string
int dayofyear = Convert.ToInt32(s.Substring(2));
// Get day of years part from your string
DateTime dt = new DateTime(1999 + year, 12, 18, new JulianCalendar());
// Initialize a new DateTime one day before year value. 
// Added 1999 to year part because it makes 5 AD as a year if we don't.
// In our case, it is 2004/12/31
dt = dt.AddDays(dayofyear);
// Since we have a last day of one year before, we can add dayofyear to get exact date

I initialized this new DateTime(.. part with 18th December because

From Julian Calendar

Consequently, the Julian calendar is currently 13 days behind the
Gregorian calendar; for instance, 1 January in the Julian calendar is
14 January in the Gregorian.

And you can format your dt like;

dt.ToString("MMddyy", CultureInfo.InvariantCulture) //123105

I honestly didn’t like this way but this is the only one I can imagine as a solution.

Accepted Answer