Two Calendar & Pesach Curiosities

Lester Kershenbaum

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Curiosity number 1:

As I sit here in the middle of February writing my little article for the shul magazine, I feel confident that, this year especially, between now and Pesach, many other articles will be written about the Jewish calendar. Why do I feel that way? It’s because this year, the first day of Pesach falls about as late in April (the 24th) as it ever has done before and people are bound to ask, “Why is Pesach so late this year?” Well, this may not be just an “accident” as I will show below.

Most of us are aware of the remarkable nature of the Jewish calendar and its accuracy. Tradition says that it was formalised by Hillel almost 2000 years ago (before the invention of sophisticated astronomical instruments), but most scholars feel that it was finally universally adopted around the time of Saadyah Gaon over 1000 years ago. The Jewish calendar has its months dictated by the phases of the moon, but manages to keep in tune with the solar year by adding an extra “leap month” for 7 individual years within the repeating 19 year cycle. This arrangement ensures that Pesach falls in early spring, as required by the Torah! (It also adds or removes a day in the autumn months of Cheshvan and/or Kislev to ensure that holidays do not fall on inconvenient days of the week – like Yom Kippur on Friday or Sunday, etc. – but that need not concern us now). Considering that the formulas for calculating the calendar was devised close to 2000 years ago, it is remarkably accurate.

BUT, it is not exactly accurate in keeping to the solar year; the length of the 19 year cycle in the Jewish calendar is approximately 2 hours longer than 19 solar years! This effect is not noticeable in anybody’s lifetime; but the reality is that the “average” date of the first day of Pesach (relative to the first day of spring) is now 4 days later than it was 1000 years ago! And it will continue to fall later on average during the next 1000 years. So, while Pesach still falls in early spring and remains “Chag Ha’Aviv” (spring festival), something will have to be done within the next few thousand years to ensure that it continues to remain so! Given the time that it takes for Jewish authorities to agree on anything, it could well take them that long to decide what to do.

Curiosity number 2:

The structure of the calendar and how it is formulated is too technical to discuss here. But, it is interesting to note that the “irregularities” in the calendar – extra days in certain months and extra months in certain years – are all to be found between Rosh Hashanah and Pesach (actually between Succot and Purim,). In contrast, between Pesach and Rosh Hashanah, the calendar is completely “regular”. So if you know which day of the week the first day of Pesach falls, you can, for example, immediately know which day of the week Yom Kippur will be on.

But the curiosity is that if you write the days of Pesach in order and write alongside them the corresponding letters of the Hebrew alphabet backwards (beginning from the end), you get an indication of the day of the week other holidays will fall – the first letter of the holiday corresponds to that letter in the (backwards) Hebrew alphabet. Thus, Tisha B’Av always falls on the same day of the week as the 1st day of Pesach, Rosh Hashanah always falls on the same day as the 3rd day of Pesach, etc.

Pesach / ↑ / Other holiday occurring on the same day of the week
א / 1st day / ת / (ת :T) Tisha B’Av
ב / 2nd day / ש / (ש :Sh) Shavuot
ג / 3rd day / ר / (ר :R) Rosh Hashanah (AND first day of Succot)
ד / 4th day / ק / no obvious holidays
ה / 5th day / צ / (צ :Tz) Tzom (Fast of) Yom Kippur
ו / 6th day / פ / (פ :P) Purim (a month before Pesach)

Curious, isn’t it?

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