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c#gregorian-calendarjulian-date

Julian Time stamp to Date Time

I am trying to convert to Julian Time Stamp to Date Time. I have the following microseconds time stamp 212302469304212709. As i understand i need to add these milliseconds to the beginning of Julian Calendar (January 1, 4713 B.C., 12:00 (noon)). So i have the following method:

private DateTime GetDateTime(string julianTimeStamp)
{
   var julianMilliseconds = Convert.ToDouble(julianTimeStamp)/1000;

   var beginningOfTimes = new DateTime(1, 1, 1, 0, 0, 0, 0);

   var dateTime = beginningOfTimes.AddMilliseconds(julianMilliseconds).AddYears(-4713).AddMonths(-1).AddDays(-1).AddHours(-12);

   return dateTime;
}

Assume i pass 212302469304212709 string as the parameter. The expected result should be 2015/07(July)/01 00:08:24.212. Based on my method, i have almost the same result, but day is not 1, it is 6. Same problem for different time stamps i tested. Could any one tell me what i am doing wrong? Thanks in advance.

Edited: This is the exact date time i expect to receive: 2015(year) 7(month) 1(day) 0(hour) 8(minute) 24(second) 212(millisecond) 709(microsecond)

Solution

  • The given timestamp 212,302,469,304,212,709 μs when converted to days (just divide by 86,400,000,000) gives 2457204.505836 days (to six decimal places, which is the best I can do without a lot of extra trouble). Using the Multi Year Computer Interactive Almanac (MICA) written by the United States Naval Observatory, and putting in the free form date 2015(year) 7(month) 1(day) 0(hour) 8(minute) 24(second) 212(millisecond) 709(microsecond), the program calculates exactly the same day count (to six decimal places), proving the time stamp is an accurate Julian date.

    One problem with the OP's calculation is trying to use the DateTime class before the earliest supported date, as pointed out by another poster. Also, the OP didn't say if 1 July 2015 was in the Julian or Gregorian calendar, but the MICA calculation proves it is in the Gregorian calendar. Since the OP is working in the Gregorian calendar, the epoch of Julian dates should be stated in the Gregorian proleptic calendar: Noon Universal Time, November 24, 4714 BC. The oft-quoted date January 1, 4713 BC is a proleptic Julian calendar date.

    "Proleptic" means a date has been found by beginning at a modern date, who's calendar date is known with absolute certainty, and applying the rules of the chosen calendar backward until the desired date is reached, even though the desired date is before the chosen calendar was invented.