Dieter Egger @ FESG TUM
Julian Date - Calendar Date

You may enter Calendar Date or Julian Date (Julian Day Number) (both referred to Greenwich). Leave the cursor in the text field which shall be your input. The six text fields on the left side represent calendar date whereas the three on the right side represent julian date. The conversion is done as soon as you hit Return or press one of the buttons.

Some important remarks apply to the conversion routines

  • since 15 Oct 1582 they represent Gregorian calendar
  • before 15 Oct 1582 they represent Julian Calendar; this implies a Julian Calendar even for times when nobody knew about it (proleptic Julian Calendar)
  • there is a gap of ten days between 4 Oct 1582 and 15 Oct 1582, meaning that the 15th of October was directly following the 4th of October (Pope Gregor forced this in order to achieve better agreement between the civil and the astronomical calendar)

More information about the history of calendars is available online.

It will not matter if you enter unvalid dates such as 234 for Day, 1 for Month and 1996 for the Year. This will be treated as the 234th January of the year 1996, just meaning the 234th day of the year. And that's the same as the 203rd February and so on.
The same applies to time values. You may leave hours and minutes empty and enter 72000 in the textfield Second. This will be converted to 20 hours, zero minutes and zero seconds. Go and play around with this feature. After hitting Return you'll find correct dates anyway.


Dieter Egger,  last update 2002-02-26