Hebrew calendar

Jewish calendar, showing Adar II between 1927 and 1948

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Hebrew Calendar (Luach)

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Hebrew calendar is a lunisolar calendar used primarily for Jewish religious observances. It determines the dates for Jewish holidays, the appropriate public reading of Torah portions, Yahrzeit (dates to commemorate the death of a relative), and the daily Psalms to be read. The Hebrew calendar is also used in Israel for civil purposes, alongside the Gregorian calendar.

Structure and Features

The Hebrew calendar is lunisolar, which means it is based on both the moon's phases and the solar year. A typical year in the Hebrew calendar has 12 lunar months, but because a lunar year is about 11 days shorter than a solar year, an extra month is added seven times in a 19-year cycle. This practice is known as leap years or pregnant years in the Hebrew calendar.

Months

The months in the Hebrew calendar are: Nisan, Iyar, Sivan, Tammuz, Av, Elul, Tishrei, Cheshvan, Kislev, Tevet, Shevat, and Adar. In leap years, an additional month, Adar II, is added after Adar, which is then referred to as Adar I.

Days

Days in the Hebrew calendar begin at sunset, not at midnight. A day is divided into 24 hours, but the hours vary in length: they are longer in the summer and shorter in the winter. This is because the hours are calculated as 1/12th of the time from sunrise to sunset or from sunset to sunrise.

Years

Years are counted from what is believed to be the year of the creation of the world, according to the Hebrew calendar. This epoch is designated as Anno Mundi (AM). The year 2023 in the Gregorian calendar corresponds to the Hebrew year 5783–5784.

Calculation

The Hebrew calendar's years and months are determined by complex calculations involving the moon's phases and the solar cycle. The calendar aims to align the lunar months with the solar year, ensuring that the Jewish festivals, most of which are agricultural and seasonally based, fall in their proper seasons.

Rosh Hashanah

The beginning of the year, Rosh Hashanah, is set according to the first new moon of the lunar month of Tishrei. However, the exact date can be adjusted by a day or two based on a set of rules designed to prevent certain holidays from falling on certain days of the week.

Leap Years

The 19-year Metonic cycle is used to determine when a leap year will occur in the Hebrew calendar. This cycle includes 12 common years and 7 leap years.

Significance and Observances

The Hebrew calendar plays a crucial role in Jewish life and ritual. Major Jewish holidays such as Passover, Shavuot, Sukkot, Rosh Hashanah, Yom Kippur, and Hanukkah are determined by the Hebrew calendar. The calendar not only dictates the timing of religious observances but also has a profound impact on Jewish culture and traditions.

Modern Use

While the Gregorian calendar is the primary calendar used for civil purposes worldwide, including in Israel, the Hebrew calendar remains significant for determining Jewish religious observances. It is also used by many Jewish communities around the world for cultural and religious purposes.