Wednesday, February 29, 2012

Leap Day

On the civil calendar, today's date, February 29, comes once in four years. Those years are always Summer Olympics and, in the United States, presidential election years. The day and the calendar have an interesting history, and one that is marginally relevant to Jewish ritual. The ancients noted that the solar year does not consist of a whole number of days; 365 is too few and 366 too many. They estimated the true year to consist of 365.25 days, and intercalated a leap day every four years to synchronize the calendar with the actual motion of the earth around the sun. They also believed that the sun revolved around the earth, and when that was proven false in the sixteenth century a few gedolim of the time announced that the new heliocentric model was heretical. Plus ca change, plus la meme chose (see also here). This intercalation became known as the Julian Calendar, promulgated by Julius Caesar, and was used throughout the Christian world until the sixteenth century. The problem was that the period of earth's rotation is not exactly 365-1/4 days. The year was too long by several minutes, leading to an error of a day roughly every century-and-a-third. Astronomers observed that the solstices and equinoxes were occurring earlier than they used to, and farmers noted that the agricultural seasons - planting, harvest, sheep-shearing and the like - were falling behind. Already in the eighth century, the Venerable Bede, an English monk, calculated the error and proposed a solution, but nothing was done until 1582, when Pope Gregory XII promulgated the calendar that bears his name. All Catholic countries immediately adopted the new calendar, but it spread more slowly in Protestant countries including England and its American colonies, where it was adopted in 1752. Thus, dates prior to that are designated "Old Style" and followed by the "New Style" equivalent. George Washington, for instance, was born on February 11, Old Style or February 22, New Style. Russia did not adopt the Gregorian Calendar until after the Bolshevik Revolution, and it is now in use throughout the world, at least for commercial and business purposes. Most Eastern Orthodox churches still use the Julian calendar, so Orthodox Christmas, for example, comes on Janurary 6 on the Gregorian calendar. Besides advancing the date by eleven days (in 1752), the calendar mandates that century years (those that end with two zeros) are not leap years even though they are divisible by four, unless they are divisible by 400. Thus, as most of us remember, 2000 was a leap year. As we do not remember, 1800 and 1900 were not. The upcoming century year, 2100, will not be a leap year. Most of us, and most of our children, will not be around then. However, children born in the coming decades, our grandchildren and great-grandchildren, will be. Given the attentiveness of most of our children to math, especially in yeshivot, I expect schools to have a tough time teaching children why 2100 is not a leap year.
The Jewish calendar was promulgated by Hillel II in the fourth century C.E., when the Byzantines (Christian Romans) ruled Eretz Yisrael, which they had been calling Palestine for three centuries. The Byzantines were still on the Julian Calendar. The date we begin to say tal umatar was fixed as 60 days after the autumnal equinox, so it fell out of sync as the autumnal equinox did. In the 20th and 21st centuries the date was December 4 or, in years before a civil leap year, December 5. After 2100 it will be December 5 or 6, unless a reestablished Sanhedrin rules otherwise.
The Jewish calendar has a similar problem. It is a bit too long and Pesah, which needs to be in "the month of spring," is slowly drifting toward summer. This is beginning to be noticeable in some Jewish leap years when the first day of Pesah is more than a month after the spring equinox, and/or the last day of Pesah is May 1. A number of solutions have been proposed. One is a return to observational determination of Rosh Hodesh and leap years; the Karaites still do this. To me this is not practical, since housewives (sorry, homemakers) need to know more than a month in advance, when Pesah comes and business people and calendar printers need to know the civil dates of Jewish holidays several years in advance. Any solution will require a Sanhedrin to promulgate; may we soon have the unity necessary to reestablish the Sanhedrin and fix what is broken.

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