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Home » The Jewish Calendar

The Jewish Calendar: A Basic Overview

Submitted by on November 6, 2005 – 3:28 amNo Comment | 26,612 views

The Leap Year

The Jewish religion has its own calendar with an independent system of months and dates. The Jewish calendar follows the lunar cycle and is, on average, eleven days longer then the solar calendar. To adjust the Hebrew and secular calendars a complex system of leap years was
established. On a Jewish leap year an additional month is added to the calendar. This occurs approximately once every three years or seven
times in a nineteen year cycle.

The significance of calibrating the two calendars lies in the Passover holiday. Passover falls on the fifteenth of the Hebrew month, Nissan. The Torah instructs us to celebrate Passover during the spring season. We must therefore ensure that the Hebrew calendar is always aligned with the calendar that governs the seasons so that the month of Nissan always falls in the spring.

When we speak of the spring season we refer to the weather patterns in Israel, the seat of the Jewish religion. Of course the hemisphere and climate of every locale govern the season in which the month of Nissan falls.

The leap year system was established by G-d and given to Moses on Mt. Sinai, as part of the Oral Tradition, and Moses taught it to the Jewish people. The actual governance of the calendar was in the purview of the Sanhedrin, supreme Jewish court, of every generation. Shortly before the termination of the Sanhedreic system, Hillel the great, committed this calendar to paper in 4120. (360 CE).

The dates for the Jewish holidays always follow the Hebrew calendar. Since the two calendars do not coincide with each other, the secular dates for the Jewish holidays vary from year to year. To discern the proper date for the Jewish holidays one must refer to both calendars simultaneously.

Extended Holidays on the Hebrew Calendar

According to the Hebrew calendar, a month is roughly twenty-nine and a half days. For this reason half the months of the year have twenty-nine days and the other half have thirty days. In ancient times, it was also the Sanhedrin’s responsibility to determine the precise number of days for
every month.

According to Jewish law, the actual sighting of a new moon is what determines the number of days in a given month. On the twenty-ninth day of every month, the high court would convene to hear testimony from witnesses who claimed to have sighted the new moon.
As soon as they
received valid testimony from two Kosher witnesses, they would effectively declare a new month and that day would be considered Rosh Chodesh (the first of the new month). If, however, witnesses would not appear, the day in question would be considered the thirtieth day of
the previous month and the next day would automatically be declared Rosh Chodesh.

To celebrate the holidays in their proper time, Jews throughout the land were required to know the precise day of Rosh Chodesh. For this reason, an elaborate system was devised. Coded flags were waved from specific mountaintops in order to telegraph the message to outlying cities and towns.

Nevertheless, Jews around the world were often unable to ascertain the exact date, in time for the holidays. Our sages therefore declared that all holidays celebrated outside of Israel should be extended for one extra day. In modern day the Sanhedrin is no longer active. Jews universally follow the calendar recorded by Hillel the great, and in this way, avoid confusion. However, in respect to ancient tradition Jewish communities outside of Israel continue to observe an additional day. The extra day is celebrated on the holidays of Sukkos, Passover and Shavuot.