Conversion of Julian Date to Calendar Date and vice versa

In the following applet you may enter Calendar Date or Julian Date (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.

You may enter julian epochs (i.e. J2000, length of the year is 365.25 days) or besselian epochs (i.e. B1950 or B1950.0, length of the year is the tropical year with about 365.2422 days, see classAconst.html) in the field Day. If the epoch is entered without decimal point, don't forget to clear the field for Month or set it to zero to deliver the correct julian day number.

If your browser does not support JAVA the following field will remain empty!

The basic Java-classes of this applet are collected in a package called "mie", meaning something like "my internet edition" or alike. If you want to use them locally, let them find their way into a directory called "mie".

Description of class Aconst used in the applet.
Description of class JulianTime used in the applet.
Description of class CalendarDate used in the applet.

OK, but I prefer to download a local copy of sources, classes and html-files!
(representing the previous version of the calendar applet with a slightly different GUI)

Dieter Egger Last Update 1997-06-27