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Introduction to the Jewish Calendar

Introduction to the Jewish Calendar


Since Biblical times, various astronomical phenomena have been used to establish uniquely Jewish definitions for the day and its hours, the months and the year.

The length of days and hours vary by the season, controlled by the times of sunset, nightfall, dawn and sunrise. The months and years of the Jewish calendar are established by the cycles of the moon and the sun.

Though the months follow the lunar cycle, the lunar months must always align themselves with the seasons of the year, which are governed by the sun. Thus, the Jewish calendar is "Luni-Solar." The discrepancy between the solar year (365 days) and the lunar year (354 days) was resolved by every so often adding a thirteenth month to the year, to form a "leap year."

In the early times of our history, the High Court (Sanhedrin) in Jerusalem was assigned the tasks of determining the beginning of each month and the balancing of the solar with the lunar years. They relied on direct observation of the New Moon, astronomical data, and other considerations.

In the fourth century after the Temple's destruction, however, when oppression and persecution threatened the continued existence of the Court, a fixed calendar was instituted -- based on the Sanhedrin's closely guarded secrets of calendric calculation. This is the permanent calendar according to which the New Moons and festivals are calculated and celebrated today by Jews all over the world.

Like the original system of observation, it is based on the Luni-Solar principle. It also applies certain rules by which complex astronomical calculations are combined with the religious requirements into an amazingly precise system.

The following pages will provide a brief digest of the factors which control the determination of the Jewish hour, day, month and year.

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Discussion (35)
December 15, 2014
Rosh Hashanah (the first day of the seventh month) is the head of the year, while Nissan (the month in which Passover falls, is the first of the months. See Our Other Head for why this is so. Staff
December 5, 2014
First month doesn't mark the New Year?
Why does the Jewish New Year coincide with September when the first month usually coincides with April?
December 2, 2014
To Susara
The Jewish New Year usually coincides with September. Staff
November 27, 2014
when does the Jewish New Year start in relation to our Gregorian calendar?
Pretoria South Africa
June 10, 2014
Jubilee Year
Thank you for your prompt answer. Is the Jubilee Year still observed? When will it occur next?
June 10, 2014
To Paul
The upcoming Jewish calendar year, Rosh Hashanah, will be a Sabbatical year. Staff
June 9, 2014
Sabbath years and the Year of Jubilee
I am goyim, so I am not at all in touch with the larger cycles of the Jewish calendar. Is a Sabbath year and/or the Year of Jubilee going to occur in the next few years? I am trying to research an apocalyptic claim that was made based on these two events.
May 24, 2014
Perhaps G-D is undecided on when "the end of time is' thus it can't be calculated.
Di Barkas
January 26, 2014
can the jewish calander be used to calulate the end time
January 21, 2013
Hebrew date for Yahrzeit on leap year
Was there a ruling or law or discussion in the past about what Hebrew date to use if the Yahrzeit date was on 30 Adar I and it is now not a leap year?
Los Angeles, CA
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