The Hebrew Calendar

One of the oldest calendars in continuous use is the Hebrew Calendar. It was not just a way of counting days to get through a solar cycle, however. It was also a constant reminder of the relationship between God and his creations, given that rituals and celebrations were not to be ignored or performed arbitrarily.

Jewish scholars attempted to determine the year based on the creation of the world after counting the genealogies in the Torah. By the 4th century CE it was decided that the world began in what the Christian world would call 3761/0 BC.

Because of Genesis 1:5 ("There was evening and there was morning, one day"), it was clear that the day begins with evening, and so sunset is the start of a new day, and the day ends with the following sunset. Festival days begin at sunset. (The International Date Line observed by much of the world creates some debate for the Jewish calendar.)

Because the Jewish calendar follows lunar cycles, each month begins with the new moon—easy to observe. This does not account for the extra days it takes for the Earth to go around the Sun, however, so between the years 70 and 1178 CE, a series of mathematical formulae were devised to try to keep up.

The "New Year" has more than one meaning in the Jewish calendar. The 1st day of the month of Tishrei is Rosh Hashanah and the start of the civil year. The 1st of Nisan, however is the start of the ecclesiastical year, the date from which festivals are counted. This puts Passover (14 Nisan) in the "first month" and Rosh Hashanah in the 7th, despite the sentence above.

Leap months have to be added every 19 years. Sometimes the year's length has to be altered by adding or removing a day from a month. When this is done, the danger is that Rosh Hashanah's day has shifted. There are important rules for making sure Rosh Hashanah is honored properly.

The man who studied the calendar carefully and helped determine many of its features that help decide when events take place was Nahshon ben Zadok, head of the Academy of Sura in the 9th century. We'll talk about him next time.

If you want a more detailed version of the Gregorian/Jewish image above, see this one.