Date calculator

Use this Java applet to calculate:
  1. Days between dates. Enter the first date, then the second date, then click the = at days between dates. Example: The number of days between Thanksgiving (11/27/2003) and Christmas (12/25/2003) this year is 174 days.
  2. Date a given number of days forward from another date. Enter the first date, then the number of days between dates, then click = for the second date. Example: If I buy a couch today (10/2/2003) and have 90 days to pay, then my payment is due on or before 12/31/2003.
  3. Date a given number of days backward from another date. Enter the second date, then the number of days between dates, then click = for the first date.
  4. Day of the week on a given date. Enter the date in first date (or second date) and press the enter key. Read the date description in first date is (or second date is). Example: Abraham Lincoln gave his Gettysburg Address on 19 Nov 1863, a Thursday.
  5. Julian day number for a given date. Enter the date in first date (or second date) and press the enter key. Read the date description in first date is (or second date is). 
Notes:
  1. Two digit dates. Don't use them. The year "99" is the same as "0099".
  2. B.C. dates. In the Julian Calendar, 1 B.C. immediately preceded 1 A.D. There was no year 0. However, the applet uses a year 0, which is really 1 B.C. For B.C. dates, you have to remember that the years are off by one--10 B.C. to the applet is really 11 B.C.  Now, this won't be much of a loss, because the Julian calendar only began in 45 B.C. and exact B.C. dates are a little hard to come by anyway. But suppose you want to calculate the number of days from the day Julius Caesar was assassinated (15 Mar 44 B.C.) to the day fire broke out in the Circus Maximus to destroy Rome (18 July 64 A.D.). Enter 3/15/43 (not 44!) B.C. and 7/18/64 A.D., to learn that there were 39208 days between those events.
  3. B.C. leap years. The Romans made a mess of this. The applet assumes that B.C. leap years are all those evenly divisible by 4. (Where 1 B.C. is considered to be year 0.)
  4. Non-standard countries. The official Julian-to-Gregorian calendar caused 4 Oct 1582 to be immediately followed by 15 Oct 1582, but only Italy, Poland, Portugal, and Spain observed this change. Other countries now using the Gregorian calendar made the switch at different times. My state of Illinois was at the time a colony of France, and made the switch later--9 Dec 1582 was followed by 20 Dec 1582. To account for non-standard calendar changes, click the Options button and enter the last date of the Julian calendar and the first date of the Gregorian calendar for the particular country of interest. Claus Tøndering (http://www.tondering.dk/claus/calendar.html) has compiled a list of various country-specific calendar changes.
  5. Today's date. When the applet is first initialized it reads the current date from the server. Of course, this is the current date where the server is, not necessarily where you are. If it is incorrect, click the Reset button to use your own computer's date.
  6. Limitations. Only dates from 1 Jan 4713 B.C. to 1 Jan 3266 A.D. are allowed. Dates prior to 45 B.C. are in the "Julian Proleptic Calendar", convenient for modern dating, but not used by any ancient peoples.

Last revised 2 Oct 2003
M. Steven Evans [ mail | home page