Happy Shabbos, 25th of Tevet, 5771! I suppose no one is celebrating on that account. In that case, Happy New (Calendar) Year! We Jews actually have two other such days in our year - one celebrating the beginning of the world (1st of Tishrei, in the fall) and one marking the beginning of the Jewish calendar year (1st of Nissan, in the spring). A number of other "new years" are part of our tradition, including Tu B'Shevat, the "new year" for trees and tithes of produce, which falls on the 15th of Shevat, and 1st of Elul, which is a "new year" for tithes of cattle, and others.
Needless to say, Jewish tradition asks the question which I know is foremost on your mind. Namely, why didn't the calendar begin with the creation of the world itself, or with the first signs of life (plants and vegetation), or animal life, for that matter? Must we be so pompous and presumptuous, narcissistic really, as to assume that all of the universe revolves around humanity's creation? In fact we are, at least some of us, and we have good reason to be, for it, meaning the universe, does revolve around us! The entire world was like an orderly table, beautifully covered, ordained and set for our arrival. A dinner party doesn't start without guests. As the focal point for all of Creation, what sense was there in starting the clock prior to our arrival?
The Jewish calendar system is relatively complicated and deserves a post of its own, and while I had intended to write of something else, now is as good a time as any. While much of the world uses the Gregorian calendar, which is solar, and some cultures and religions (such as Arabs and Islam) use the lunar calendar, we Jews use both - the solilunar calendar, or the lunisolar calendar. How so?
The Jewish year is the solar year, while the Jewish months are lunar months. Say what? To understand the difference, it's helpful to understand how the other calendars work. The Gregorian calendar, which replaced the Julian calendar, is the normal calendar used by most people in the world for day to day life, commerce, etc. Being a solar calendar, it is based on the movement of the earth around the sun, or of the sun around the earth, for all you relativity nerds. Once it was established that the solar year is almost exactly 365 days, the year was divided, relatively neatly, into twelve months. It's not a perfect calendar, mind you, with leap years and such, but it works fairly well.
Working poorly, in this case, would be a calendar that claimed it was summer while the snow was blowing, or spring when the leaves were wilting and falling off trees. Our calendar works so well that we've actually mentally fixed and take for granted that the months and seasons correspond to the respective climatic conditions with which they coincidence. It's warm in the Summer, which stretches (roughly) from June through August, and most cold in the Winter months of December through February, at least in the Northern Hemisphere. It's worth pointing out that today, it's difficult for people to conceive of a calendar working "poorly", but that was not so uncommon in antiquity.
Take the Islamic calendar, for example. It is a purely lunar calendar. Anyone who is Muslim, or has a Muslim friend or a close significant other, or merely studied the Islamic calendar, knows that Islamic holidays - which naturally reoccur on a yearly cycle - do not coincide year to year. Instead, holidays like Ramadan retreat a few days each year. Ramadan began on August 11th this year. Ramadan will begin August 1st in 2011, July 20th in 2012, July 9th in 2013, June 28th in 2014, June 18th in 2015 and so on, looping backwards around the Gregorian calendar year. I think the Muslim calendar has leap years, but I'm not familiar with how often they occur. However, such calendar variation poses no problem for Muslims, for while holidays like Ramadan place certain dietary restrictions on followers of Islam - it's a 30 day sunrise to sunset fast - they have no seasonal significance that I'm aware of. The reason for such variation, year to year, is that the monthly lunar cycle does not coincide perfectly with the solar cycle.
Jewish festivals, particularly biblical ones - Passover, Shavuot, and Sukkot - are intrinsically tied to seasonal changes. The Torah specifically commands us, "Guard the month of the spring, and make the Passover offering." (Devarim 16:1) Meaning, Passover must come in the spring. Similarly, Shavuot is the festival of the First Fruits. A country close enough to the equator, like Israel, has two growing seasons. Crops can be planted in the early spring, and will yield their first fruits by late spring or early summer. Likewise, Sukkot, which comes in the autumn, is a harvest festival. It wouldn't make much sense to celebrate a harvest festival in the middle of summer's heat, or winter's cold, when nothing is being harvested. A purely lunar calendar, like that used by the Arabs, would throw the timing of Jewish festivals into a tailspin. It would seem natural for us Jews to use a solar calendar, which registers the position of the sun relative to the earth, thus enabling the accurate keeping of seasons, and seasonal festivals.
Nevertheless, we Jews do use the lunar calendar, for reasons that are beyond the subject of this post. In doing so, however, we must make a series of adjustments to keep the monthly lunar cycle attuned to the solar month. Here's how our calendar works, in simplified form. The main problem was that while the solar month divides out to about 30 days, the lunar months are approximately 29.5 days. This difference seems small, until you multiply by twelve months, at which point the lunar year is a mere 354 days, about eleven days short of the solar cycle! (If you look back at the Ramadan dates, the pattern of around 11 days being subtracted, year to year, now begins to make sense.) So, how does the Jewish law resolve this dilemma? When the going gets tough, the tough get pregnant.
Every three years or so, we add an entire additional month to the Jewish year, called Adar Sheini, commonly seen in literature as "Adar II", the second month of Adar, which follows the regular month of Adar ("Adar Rishon"), sometime in the spring. These years, which we might refer to as leap years, are termed "pregnant" in Jewish tradition - shanah meuberet. Other adjustments abound, with some years termed "complete" and others "incomplete", resulting in an addition or subtraction of days from certain months. In addition, minute postponements can be made to festivals, to make sure they don't fall on certain days. Yom Kippur, for example, is not allowed to fall on the day before or after a Shabbat.
When the seat of centralized Jewish leadership was still in our historic and spiritual homeland, and the Great Sanhedrin - the supreme Rabbinic court - ruled in Jerusalem, no systemic calendar was effect. Jewish months and years were set by the court, relying on seasonal variation (such as the growth of crops) and the reports of witnesses to note changes in the moon's disposition as it moved through its cycle. Even after the Romans twice destroyed Judea (in 70 CE and 135 CE), sacked Jerusalem, destroyed the Temple and murdered millions of Jews, while enslaving and dispersing hundreds of thousand more, the Sanhedrin continued to operate, often under conditions of persecution, for another two hundred years. It's last official act, in 358 CE, under the authority of Hillel, the Nassi - the Prince or leader of the court - was to establish the permanent Jewish calendar that we use to this day.
The "modern" Jewish calendar follows a 19-year cycle, apparently first noted by Meton of Athens, and thereby called the Metonic Cycle. It marks a near perfect coinciding between the lunar and solar calendars every 19 years. In practice, it means that the Jewish calendar experiences a "pregnant" year on the 3rd, 6th, 8th, 11th, 14th, 17th, and the 19th years - seven leap years in all. In this way, the lunar monthly cycle is kept in alignment with the solar year, and Jewish holidays are firmly anchored in the seasons for which they were meant.
So with that, Happy New Tax Year!