Each day is labeled with the day-of-the-year as well as the day-of-the-month. This helps when you use the the ISO-8601 standard http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html . For example, the 2 standard formats for Monday, March 3, 2000 A.D. are:
2000-061 2000-03-03.
http://www.stud.unit.no/USERBIN/steffent/home.pl has a World Clock and more calendars.
http://www.execpc.com/~mikeber/calendar.html is a little more interactive.
I have more information about time ../html/time.html . [FIXME: move most of this info to time.html; leave only source, a link to time.html, and relevant comments here]
[ Todo: improve my calendar using code from http://www.execpc.com/~mikeber/calendar.html Make my calendar link to that page and to the ISO-8601 standard http://www.ft.uni-erlangen.de/~mskuhn/iso-time.html, ]
Royal Greenwich Observatory http://www.ast.cam.ac.uk/RGO/leaflets/leapyear/leapyear.html which would appear to be the authoritative reference on calendars, says "Pope Gregory XIII, in 1582, instituted the Gregorian calendar, which has been used since then. ... 1800 and 1900 are not leap-years whereas 2000 will be."
2000/01/01 THE YEAR 2000 starts. Saturday. 2000/02/29 leap day 2000/12/31 366th day of year.
http://www.boutell.com/birthday.cgi/ "See who's celebrating a birthday today; find birthdays for any day of the year with the Global Birthday Navigator (GBN); and add your birthday via the Universal Birthday Form (UBF)."
an example of a nice calendar with both day-of-year and days-remaining-in-year (Jan 1 is day 1/364) (Dec 31 is labeled 364/1). http://pgh.nauticom.net/cgi-bin/execute/babylon/webcal.pl/
day of the week http://www.geocities.com/SiliconValley/2499/code.html has 2 nifty procedures for calculating the day-of-week for any year-month-day, one for humans (in your head, without paper), and one for machines.
Calendar Zone http://calendarzone.com/
Calendar Program (mocal) in PostScript http://www.o--o.net/comp/ps/mocal.php
Calendar Program in PostScript that folds up to a dodecahedron. http://www.o--o.net/comp/ps/cal.php
"Martian Clock and Calendar" Copyright © 1997, 1998 by Mickey D. Schmidt http://pweb.jps.net/~tgangale/mars/other/schmidt.htm points to "Martian Calendar" by Anton Sherwood http://pweb.jps.net/~tgangale/mars/other/sherwood.htm
http://c2.com/cgi/wiki?PerpetualCalendarAlgorithm
Julian Day Number also called Astronomical Julian Day (AJD). http://en.wikipedia.org/wiki/Julian_day Jan. 1, 2000 = MJD 51,544 ... January 1, 4713 BC
http://myfreecalendarmaker.com/
In Java, one should consider using the "Calendar" class or its subclass "GregorianCalendar" .
Generate an HTML Calendar http://www.markworld.com/makecalendar.html
1997-01-20:DAV:Started
by David Cary d.cary@ieee.org
end http://www.ionet.net/~caryd_osu/david/program/calendar.html