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Hebrew calendar



The Hebrew calendar (Hebrew: הלוחהעברי) or Jewish calendar is the calendar used by Jews for religious purposes. It is a lunisolar calendar used to reckon the Jewish New Year and to determine the dates for Jewish holidays, the appropriate Torah portions, for public reading, and which daily Psalm is to be read, among many ceremonial uses. Originally the Hebrew calendar was used by Jews for all quotidian purposes, but by the era of the Roman occupation (1st Century BCE), Jews were compelled to follow the imperial civil calendar for all civic matters such as the payment of taxes and dealings with government officials.

The Hebrew calendar's epoch (reference date), 1 Tishrei 1 anno mundi, is equivalent to Monday, October 7, 3761 BCE in the proleptic Julian calendar. Two major forms of the calendar have been used. Before the destruction of the Second Temple in 70 CE, the calendar was observational, with the beginning of each month determined by the testimony of witnesses who had observed a new crescent moon. Between 70 and 1178 CE a rule-based fixed-arithmetic lunisolar calendar system was adopted to achieve the same effect.

The origins of the Hebrew calendar are found in the Torah, which refers to the existence of several numbered but un-named months in the Noahide (pre-Jewish) period, and which recounts several calendar-based commandments, including God's commandment during the Exodus from Egypt to fix the month of Nisan as the first month of the year (Exodus 12:18). The development of the calendar was likely influenced by the Babylonian exile in the 6th Century BCE, during which Babylonian names for the months were adapted; the Babylonians also employed a lunisolar calendar derived from the Sumerian calendar. Following the Jewish diaspora of Roman times (1st Century CE), calculations were increasingly used to fix dates, with the principles fully described by Maimonides in 1178 CE in the Mishneh Torah.

Because of the roughly eleven-day difference between twelve lunar months and one solar year, the year lengths of the Hebrew calendar vary in a repeating 19-year Metonic cycle of 235 lunar months, with an intercalary lunar month added every two or three years, for a total of 7 times per 19 years.

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Number

Hebrew
name

Common
name

Length
in days

Notes


1

2

3

4

5

6

7


8

9

10

11

12 *

12 / 13 **
 


נִיסָן

אייר


סיון


תמוז


אב


אלול


תשרי



חשון


כסלו


טבת


שבת


אדר


אדר


Nissan

Iyar

Sivan

Tamuz

Av

Ellul

Tichrei


Cheshvan

Kislev

Tevet

Shevat

Adar1

Adar2


30

29

30

29

30

29

30


29 ou 30

29 ou 30

29

30

29

30


called Aviv and Nisan in the Tanakh

called Ziv in the Tanakh









called Eitanim in the Tanakh, Modern first month, Rosh Hashana is celebrated in Tishrei

Bul in the Tanakh







* Only in leap years

** Adar 1 is only added 7 times in 19 years. In ordinary years, Adar 2 is simply called Adar.

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