This calculator computes the date of Easter for any year after 1582 AD. The JavaScript program was adapted from a BASIC program which appeared in the Astronomical Computing column of Sky & Telescope, March, 1986.
The program is operated by entering a calendar year that is greater than 1582, and then pressing the Calculate button. All entries are cleared by pressing the Clear button. If the year is not in the valid range, the output windows will display: Invalid Year. The Next Year button increments the calendar year and recomputes the date of Easter. The Prev Year button decrements the calendar year.
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The Java Script source code for this program can be viewed by using the View|Source command of your web browser.
You may use or modify this source code in any way you find useful, provided that you agree that the author has no warranty, obligations or liability. You must determine the suitablility of this source code for your use.
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The date of Easter given here is the date used by the western Christian churches. It is computed according to the rules established as part of the Gregorian calendar reform in 1582. The Gregorian calendar is the one now used worldwide for civil purposes.
The date of Easter determines the following dates:
| Days before Easter | Days after Easter | ||
| Septuagesima | 63 | Rogation Sunday | 35 |
| Quinquagesima | 49 | Ascension | 39 |
| Ash Wednesday | 46 | Pentecost | 49 |
| Palm Sunday | 7 | Trinity Sunday | 56 |
| Good Friday | 2 | Corpus Christi | 60 |
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