The Hebrew calendar

The Hebrew calendar is lunisolar: its months follow the moon and its years are kept in step with the sun and the seasons. A month begins at the new moon and has 29 or 30 days. Twelve such months make about 354 days, eleven days short of a solar year, so a leap month is added seven times in every nineteen years.

The months

The months, from the one that begins the religious year, Nisan in spring, are Nisan, Iyar, Sivan, Tammuz, Av and Elul, then Tishrei, Cheshvan, Kislev, Tevet, Shevat and Adar. The civil year begins with Tishrei, at Rosh Hashanah. In a leap year there are two Adars, Adar I and Adar II, and Purim is kept in Adar II.

Leap years

In each 19-year cycle, years 3, 6, 8, 11, 14, 17 and 19 are leap years: you can test a Hebrew year by dividing it by 19 and checking the remainder (3, 6, 8, 11, 14, 17 or 0). For example, 5787 (September 2026 to September 2027) leaves a remainder of 11 when divided by 19, so it is a leap year of 13 months, with Adar I and Adar II.

The year number

The year count, from the traditional date of creation, was 5787 at Rosh Hashanah in September 2026. Subtract 3,760 or 3,761 to find the Gregorian year, depending on the part of the year.

Why holidays move

Because of the lunisolar scheme, the Gregorian date of each holiday varies from year to year within a window of about a month, but its Hebrew date does not change.

Jewish holidays begin at sundown on the evening before the date shown. Dates follow the standard Hebrew calendar; communities outside Israel keep a second day of several festivals. Customs differ between Orthodox, Conservative, Reform and other communities, and this is not a ruling: ask your rabbi.