Hebrew calendar


July 6, 2022

The Hebrew calendar is a lunisolar calendar, that is, calculated on both a solar and a lunar basis. The year is made up of 12 or 13 months in turn made up of 29 or 30 days. Jewish holidays are defined in relation to the Hebrew calendar: since some of these are closely related to the season, they must fall in the right season.The names of the months of the Hebrew calendar derive from the language in the Babylonian comparison, with which the Jews came into contact in the 6th century BC Originally the duration of the months was not established in advance, but the beginning of each month was fixed through the direct observation of the new Moon; in the twelfth century Maimonides codified a mathematical system that fixes the beginning of the months and the duration of the years on the basis of precise and immutable calculation rules. The Jewish calendar is a ceremonial calendar also used in the State of Israel to establish holidays. In Israel, however, it is not only ceremonial, in fact Israeli public and administrative documents and Israeli identity cards show both calendars. Israeli civil law permits the indistinct use of both calendars in contracts and in any type of documentation and it is used in daily life by the large share of the Israeli Haredi population instead of the Gregorian calendar. The current Jewish year is 5782 (Gregorian calendar: sunset of September 6, 2021 to sunset of September 25, 2022).

The cycle of years

The Hebrew calendar is based on the Metonic cycle of 19 years divided between normal and embolismic in which a thirteenth month is added. The embolismic years are the 3rd, 6th, 8th, 11th, 14th, 17th and 19th years of the cycle. This is made up of 12 years of 12 months and seven years of 13 months for a total of 235 lunar months. The thirteenth month is called Adar Sheni. The lunar month lasts approximately 29 days, 12 hours, 44 minutes and 3 seconds. The solar year, on the other hand, lasts about 365 days, 5 hours, 48 ​​minutes and 46 seconds. From this it follows that within a year the 12-month lunar calendar lags behind the solar one by about 10 days and 21 hours. By alternating years of 12 and 13 months as specified, it is possible to almost exactly compensate for the difference: the difference between 19 solar years and 235 lunar months is just about 2 hours and 5 minutes, equal to about 7 minutes per year.

The cycle of months

As for the years, the months can also have different durations to compensate for the error present in the duration of the lunar cycle. There are, therefore, the complete months (of 30 days) and the missing ones (of 29 days): generally they alternate, but there are exceptions. The sequence of the months of the Hebrew calendar is: Tishri (30 days): Sept-Oct; Cheshvan (29 or 30 days): Oct-Nov; Kislev (29 or 30 days): Nov-Dec; Tevet (29 days): Dec-Jan; Shevat (30 days): Jan-Feb; Adar (29 or 30 days): Feb-Mar / (Adar Sheni) (29 days): Mar-Apr; Nisan (30 days): Mar-Apr; Iyar (29 days): Apr-May: Sivan (30 days): May-Jun; Tammuz (29 days): Jun-Jul; Av (30 days): Jul-Aug; Elul (29 days): Aug - Sept. The month of Adar Sheni - also called Veadar - is absent in normal years and is present in embolismic years. The months of Cheshvan and Kislev vary in length depending on the type of year. Normal years can last 353, 354, or 355 days; the embolismic years 383, 384 or 385. The 19-year cycle can last from 6939 to 6942 days. The Hebrew calendar repeats itself exactly after a cycle of 689,472 years, equal to 251,827,457 days. The average length of the year is therefore approximately 365.2468 days: the deviation from the average solar year is approximately 6 minutes and 39 seconds, so the Jewish calendar lags behind by one day compared to the solar year every approximately 216 years. .

Names of the months

Both the Syrian Calendar, currently used in the Arab countries of the Fertile Crescent, and the Modern Assyrian Calendar share