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Easter is the most important single date in the Christian ecclesiastical calendar. In addition, an entire cycle of dates surrounds Easter, involving a span of over one hundred days of the year. |
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Although the calculation of the date is important to the ecclesiastical calendar, it is also important to the history of computation and mathematics. Procedures for calculating Easter date are among the first algorithms known. |
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6.2.3.1.1
Brief History of Easter |
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In this section, I outline a quick history of Easter. |
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Easter is the most important day of the Christian ecclesiastical calendar, annually celebrating the Resurrection of Christ. |
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The establishment of a date for Easter has been the source of bitter controversy for many centuries, and involves a good deal of the history of the early Christian church. In addition, the desire to calculate the date for Easter provided Western civilization with several important ideas. The entire concept of a Christian era is based upon one such endeavor. Knuth, in Fundamental Algorithms (p. 155), remarks that, "There are many indications that the sole important application of arithmetic in Europe during the Middle Ages was the calculation of Easter date, and so such algorithms are historically significant." The very concept of algorithm itself, in fact, owes a great deal to the attempt to develop systematic rules for calculating Easter date. |
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6.2.3.1.1.2
The Basis in Jewish Passover |
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In the early days of the Christian church, observance of Easter focused on the Jewish Passover, or Pesach, for several reasons. First, early Christian church calendars were derived from the Jewish calendars. Second, three of the four gospels (Mark, Luke, and Matthew, the Synoptic gospels) concur that the crucifixion of Christ occurred on the day of preparation, that is, Friday, before the Saturday (Jewish Sabbath) in the week of Passover. The fourth gospel, John, places the date a day later. |
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6.2.3.1.1.3
Jewish Calendar Background |
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The first day of the Jewish month was intended to coincide with the first visibility of the lunar crescent. This observation-based rule for defining months dates to Babylonian times and is the basis for the definition of months within the Islamic calendar today. |
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This rule causes the full moon to be taken as the 14th day of the month. Thus, the Eve of Passover falls on 14 Nisan in the Jewish calendar. The Paschal Lamb was slain and eaten in the evening. Because the Jewish day ends at sunset, the first day of the Feast of Passover begins with 15 Nisan. |
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