When is Passover?

Aramaic ThoughtsWeek of April 13 - 19, 2008
A Break for Passover

To borrow a joke, one Jewish man asks another, “When is Passover this year?” The second man answers, “14th of Nissan, same as every year.” The joke is intended to emphasize the point that the dates of the Jewish holidays are always the same in the Jewish calendar. However, the Jewish calendar does not match up precisely with our modern Gregorian calendar, so with regard to the modern calendar, the Jewish festivals occur on different dates every year.
The Gregorian calendar that is used by most of the world today is essentially a solar-year calendar. Thus, in general every four years an extra day is added in recognition of the fact that the solar year is actually about 365.25 days long.

The traditional Jewish calendar, on the other hand, takes three astronomical considerations into account. The first is, of course, that the solar year is 365.25 days long. The second consideration is that the lunar month is about 29.5 days long. The third consideration is that the solar year is approximately 12.4 lunar months long. The Jewish monthly calendar is a lunar calendar, so that all months in the Jewish calendar are either 29 or 30 days long, to match the lunar month. However, the Jewish years are sometimes 12 months long, and other times 13 months long. This latter fact is to take care of the “creep” that would otherwise occur in the Jewish year. In other words, if the Jewish lunar calendar were a consistent 12 months long, over time Passover, which is a spring festival, would gradually creep backward through the seasons, so that at some time it would occur in the winter, at some time it would occur in the fall, and at some time it would occur in the summer. In order to forestall this creep an additional month is added to the Jewish calendar about every fourth year. Another way of thinking about it is that for two or three years, Passover moves back (earlier) about eleven days each year. Then, in the year when the extra month is added, it jumps forward 29 or 30 days, and the backward creep then begins all over again. This explains why it is that Passover and Easter so rarely coincide. The two holidays are being located in time on the basis of different calendars.

In the Jewish ritual calendar Nissan (also spelled Nisan) is the first month of the year (think of it as January), and Passover occurs on the 14th of Nissan. The last month of the year, that is, the month preceding Nissan (think of it as December) is Adar. When a thirteenth month is added to the calendar, it is added before Adar, and is referred to as Adar I, Adar Rishon (beginning), or Adar Aleph (the first letter of the Hebrew alphabet). The “regular” month of Adar is referred to as Adar II, Adar Sheini (second Adar), or Adar Beit (second letter of the Hebrew alphabet). The Gregorian years 2007-2008 (the Jewish year overlaps the successive Gregorian years) parallel the Jewish year 5768, which is one of the years with a thirteenth month. Thus, Adar I began on February 7, Adar II began on March 8, and Nissan begins on April 6, thus putting Passover on April 19, 2008.

Those interested in more about the Jewish calendar can consult the web site: http://www.jewfaq.org/calendar.htm