This article originally appeared in the Jewish Free Press, Calgary

Calendar Conundrums*

Jews are well accustomed to the fact that our religious calendar marches to a completely different rhythm from the one that is in common use in the surrounding society. There is however a conspicuous exception to that pattern: The day on which we begin to pray for rain in our daily prayers (introducing the Hebrew formula "Ten tal umatar") is defined in the Siddur by a date in the "civil" calendar, the 4th (or sometimes the 5th) of December.

The origins of this anomaly go back to ancient times, when the Rabbis of Babylonia decreed that rain should not be requested prior to the sixtieth day after the Autumnal Equinox. The significance of this date is not explained in the Talmud, and some scholars have suggested that for the Babylonian farmers rainfall was considered a nuisance before the conclusion of the date-harvest. Whatever the reason, it is clear that the equinox, as a phase in the cycle of the sun, is most conveniently calculated by the civil calendar, which is a solar one.

In the course of the Middle Ages the Babylonian practice came to be accepted--though not without a struggle--by all Jewish communities outside the Holy Land. Israel itself follows a different, earlier date, defined according to the Jewish calendar (the 7th of Heshvan).

Initially many Diaspora communities followed the Israeli custom, but eventually the powerful Babylonian Rabbinate succeeded in asserting its authority as the supreme authority for religious practice.

Thus, as an eminent contemporary halakhist has observed, normative practice has rejected the more reasonable precedents of praying for rain either when it is beneficial for our own climate, or when it is required in the Holy Land--in favour of the unlikely option of linking it to the climate of Iraq (the current inhabitant of the land that was formerly called Babylonia).

But the peculiarity of the situation does not end there. The Autumnal Equinox actually occurs on the 22nd of September, so that the sixtieth day following should come out on November 20, not December 4!

The discrepancy originates in the methods that we employ for calculating the solar year. The Talmud assumes that a year consists of precisely 365 1/4 days and halakhic practice bases its calculations on that premise.

The calculation is very close, but it is not fully accurate, since an astronomical year falls eleven minutes and fourteen seconds behind that estimate. The margin is admittedly a tiny one, but when stretched across the centuries of Jewish history the minutes begin to add up. Every 128 years the Jewish reckoning pulls a full day ahead of the astronomical equinox.

The Catholic Church, aware that their traditional Julian calendar (based on the same assumptions as the Talmud's) had lost touch with the facts of nature, corrected the situation through the introduction of the Gregorian calendar in 1582, which involved turning the clocks ahead eleven days to adjust for the discrepancy! The Gregorian calendar cleverly regulates the frequency of leap-years in order to keep the equinoxes in astronomic proportion. It has now become the accepted standard for most of the world.

Because the Jewish world has never introduced an equivalent adjustment, the cumulative error over the centuries now amounts to fifteen full days.

And the gap will continue to widen. Even as Siddurim published a century ago instruct the worshippers to begin reciting "Ten tal umatar" on December 3 or 4, so in the year 2100 will the dates shift to Dec. 5 or 6--gaining three days every four hundred years.

If left uncorrected this will lead to some bizarre consequences, as the season for reciting "Ten tal umatar" keeps shrinking. Eventually it will advance all the way to Passover, which marks the termination of the rainy season, and will not be recited at all. Although this is a mathematical inevitability, don't hold your breaths. It is not scheduled to happen yet for another 35,000 years.

As often happens, the halakhic world tends to prefer its own traditional rules and definitions over ones that issue from the outside world. Some Rabbis have taken note of the problem, but are reluctant to tamper with traditions. Almost none have discerned any cause for alarm.

After all, they argue, we live in faith that the Messiah will appear at any moment. Surely he will arrive before matters get out of hand, so why don't we just wait and let him deal with the problem!

This article and many others are now included in the book

Holidays, History and HalakhahHolidays, History and Halakhah

by Jason Aronson Publishers

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[1]First Publication: Jewish Free Press, Dec. 15 1994.
  • A. and D. Lasker, "The Strange Case of December 4," Conservative Judaism 38:1 (1985), 91-9.