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The New Calendar Year

C.B. Gavant

By looking at your calendar, you know exactly when Rosh HaShanah, the first day of Tishrei, comes out. But have you ever wondered who writes those calendars? How do they know when the first of Tishrei — and all the Roshei Chodashim, Yamim Tovim, and so forth — should be?

Wednesday, September 12, 2012

calandarThe Sanhedrin’s Secret: Sod Ha’Ibbur

In the days of the Sanhedrin, which began with Moshe Rabbeinu in Mitzrayim and continued until about 1,600 years ago, each month two witnesses who had seen the new moon would appear in beis din. The beis din would listen to their testimony, decide whether to accept it, and let the rest of Klal Yisrael know that it was Rosh Chodesh — an important thing to know, because if you don’t know when Rosh Chodesh is, how will you know when to celebrate Pesach, Yom Kippur, Succos, or even your birthday?

The Sanhedrin understood the cycle of the moon and knew exactly where in the sky the moon would appear and when; they therefore knew to discount false or mistaken testimony. Their calculations, called sod ha’ibbur, were kept secret so that people wouldn’t come bearing false testimony. In order for Rosh Chodesh to be officially declared, though, they waited for witnesses, as this is how the Torah instructs us to perform the mitzvah of kiddush hachodesh, sanctifying the new moon.

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