Select any month, and enter any four-digit year (0001-9999), or use the Previous Month and Next Month buttons.
Prior to 1582, every year divisible by 4 was a leap year. Since a year contains only 365.242199 days (slightly less than 365.25 days), an error of ten days accumulated over the centuries. To compensate for this error, Pope Gregory XIII (after whom the Gregorian Calendar is named) decreed that the ten days between October 5, 1582 and October 14, 1582 would be eliminated from the calendar. This made October 1582 the shortest month, with only 21 days. After 1582, years divisible by 100 are not leap years unless they are also divisible by 400. Thus, 1900 is not a leap year, but 2000 is.
Here's the Java source code.
Please visit Herb's Calendar Wizard website, for a complete perpetual calendar and calendar calculator.
http://www.wiskit.com/calendar.html Last updated December 25, 2005 by firstname.lastname@example.org.