How Many Days in a Lunar Month?

By: Rabbi Jonathan Matt

The Jewish calendar is a lunar one, based on the 29 1/2 day revolution of the
moon around the earth. Since the time of Hillel II about 1500 years ago, the
months alternate quite regularly between 29 and 30 days. Prior to that time, the Jews followed the rule of the Mishnah that eyewitnesses testify before the
Sanhedrin (High Court) that they personally witnessed the new moon
somewhere in Israel. Efforts were made to encourage citizens to travel directly to the Sanhedrin, even on Shabbat, in order to set the calendar as precisely as possible:

"There was a large courtyard in Jerusalem called Beth Yaazek, where all the
witnesses assembled, and there the Court examined them. And they prepared large meals for them so that they might make it their habit to come...." (Mishnah Rosh HaShana 2:5)

When the testimony was accepted, the new month was declared by the Sanhedrin. How was the message passed along throughout Israel and from Israel to the Jewish community in Babylonia? That same night, signal fires were lit on the Mount of Olives in Jerusalem and from mountaintop to mountaintop the message was repeated all the way to Babylonia (modern-day Iraq!).

The Mishnah reports that at a certain stage the enemies of the Jews sent false signals. From then until the time of Hillel II, the news was sent by messenger. Thus most of the one-day Biblical holidays are celebrated even today in the Diaspora (lands outside of Israel) as two-day holidays, a remembrance of the era when the exact date would be known only ex post facto.

A YEAR OF THIRTEEN MONTHS?
The Jewish calendar is a lunar calendar, based primarily on the monthly cycle of the moon. Unfortunately, the moon is not very considerate of earthly math, and takes about 29 1/2 days to circle the earth. Furthermore, if you multiply 29.5 by 12, you'll find yourself with a year only 354 days long, 11 days short of a solar year. By using a lunar calendar, this would mean that what started out as a spring festival would gradually regress into a winter festival, then fall, summer and after about 33 years, again be in the spring. The Moslems, who also use a lunar calendar and who do not adjust for the the 11 day shortfall, find their holidays rotating around the year.

The Jewish Sages, to solve this problem, invented the leap year, but in a more drastic way than our February 29. Every two or three years the Patriarch and his Sanhedrin added an entire month in the early spring. They made the actual decision by checking out the physiology of the fruit trees in various parts of Israel.

About 1500 years ago, the Patriarch Hillel II established a system of calculations which stipulated seven leap years within each 19-year cycle, a system valid until today. How can you tell if it's a leap year without a detailed calendar? If Passover starts more than a couple of weeks after Easter, a month has just been added. If Passover ends before Easter, the following year will probably be a leap year. A similar pattern can be detected between Hanukah and Christmas.

About The Author:

Articles on Judaism: http://www.whatsjew.com/articles/

Please Rate this Article

5 out of 54 out of 53 out of 52 out of 51 out of 5 

# of Ratings = 1 | Rating = 1/5

Click the XML Icon Above to Receive Jewish Calendar Articles Via RSS!