Coming up on Tu Beshvat, yet it still feels like winter has hardly begun. We've had some rain (though not enough), the hillsides are greening, and the earliest wildflowers are just up. But the almonds aren't ready to blossom yet. The Jewish holidays, as we all know, are always either early or late, but never just on time. This year it's only a month from the winter solstice to Tu Beshvat and that would make Pesach fall just on the spring equinox (one month from solstice to Tu Beshvat, one month from Tu Beshvat to Purim, one month from Purim to Pesach). Here in the mountains of the Galilee, where we are very aware of the seasons as reflected in the flora, it is fascinating to follow the interplay of nature and calendar.
The Hebrew calendar integrates the lunar and solar cycles. Islam, originating among desert tribes, makes do with just the lunar cycle, each year consisting of 12 months of 29.5 days (a moon cycle). Thus, their year is 354 days long. Since the festivals of the Hebrew Bible relate to the agricultural cycle of the land of Israel, the Jewish calendar can't ignore the solar year which determines the seasons, and is 365.25 days long. Reconciling these two so that the two cycles stay synchronized is a bit more complicated than just adding February 29th every four years. In ancient times, when we lived a life more attuned to nature, the process of determining calendrical milestones was based largely on direct observation. Rosh Chodesh, the beginning of each month, was determined by the examination of witnesses who came in to the rabbinical court to report on the exact time of sighting the molad, the "birth" of the new moon. And the declaration of a leap year was also determined by observation, as described in the Talmud:
Our rabbis taught: A year may be declared a leap year on three grounds: on account of the premature state of the grain crop, or that of the fruit trees, or on account of the lateness of the equinox. Any two of these reasons can justify declaring a leap year, but not one alone. [but, once Rabban Gamaliel the Nasi wrote to the Diaspora communities:] We beg to inform you that the doves are still tender and the lambs still young, and the grain has not yet ripened. I have considered the matter and thought it advisable to add thirty days to the year.
-Babylonian Talmud, Sanhedrin 11b
Every year, the lunar cycle moves back against the solar cycle by 11 days (365 minus 354). Thus, if Pesach falls on April 11 one year, it will fall on April 1 the next year, then March 20, then March 9, and so on through the solar year eventually reaching December, then August, etc. Indeed, with the Moslem calendar, this is the case, and the month of Ramadan advances through the solar calendar, eventually coming back to the same season about once every 32 years. For us this is not acceptable, as Pesach, for example, is tied to the spring grain harvest of Israel; it is specifically referred to in the Torah as the spring festival. Pesach in December, or August, would be absurd. And so, every year, the rabbis would observe the progress of the spring, and if, by the time the month of Adar arrived (the month before Nisan, in which Pesach falls) it was clear that the grain would not be ready for harvest by Pesach (as well as some corroborating evidence as described in the above passage), they would insert an extra month,
Adar II, in order to delay Pesach. Eventually, just as we stopped waiting for witnesses to the new moon, and proclaimed it according to calculation, we also standardized the sequence of leap years. It turns out that the two types of year can be synchronized by adding 7 months in every cycle of 19 years; the rabbis declared that years 3, 6, 8, 11, 14, 17, and 19 of each cycle will have two Adars. It is now 5768. Divide 5768 by 19; you get 303 with a remainder of 11, so we are in the 11th year of a cycle, making this is a leap year. (This 19 year cycle means that your Gregorian birthday will fall on the Hebrew date on which you were born, on your 19th, 38th, 57th, 76th, and 95th birthdays.)
Tu Beshvat seems too early this year, but don't worry, it's a leap year: Pesach will be late.