Milwaukee North News

17 Jewish Calendar Facts

1. It Is Used to Calculate Holidays, Bar Mitzvahs, and Yahrzeits

The Jewish calendar is the structure upon which all Jewish holidays are based. The High Holidays, Sukkot, Chanukah, Purim, Passover and Shavuot are always celebrated on their specific dates on the Jewish calendar. (For example, Rosh Hashanah is always celebrated on 1–2 Tishrei, and Passover always begins on 15 Nisan.)

Other notable occasions that follow the Jewish calendar are birthdays, yahrzeits, bar mitzvahs and bat mitzvahs.

Read: How to Celebrate Your Jewish Birthday and Calculate your Jewish birthday

2. It Was Given to Moses at the Exodus

Exactly two weeks before the Exodus from Egypt, G‑d told Moses and Aaron: “This month [Nisan] shall be for you the head of the months,”1 setting into motion the Jewish calendar and its unique format. In fact, this was the very first commandment G‑d gave to Moses.

Read: 12 Facts About the Month of Nisan Every Jew Should Know

3. The Greeks Tried to Abolish It

The Chanukah story begins with the persecution of the Jews by the Syrian Greeks. Recognizing the crucial role of the calendar in Jewish life, the Greek king Antiochus decreed that the Sanhedrin was forbidden to sanctify new months (see below). Led by the Maccabees, the Jews defied the royal edict, culminating in a victory over their oppressors and the creation of a new Jewish holiday in our calendar.

Read: Why Couldn’t the Jews and Greeks Just Get Along?

4. It Follows the Lunar Cycle, But Is Still Aligned with the Seasons

Unlike the Gregorian calendar, which follows the solar cycle (of about 365.25 days), the Jewish calendar follows the lunar cycle, which means that the year is comprised of 12 lunar months (of approximately 29.5 days each).

Nevertheless, the Jewish calendar is not solely lunar. Due to the 11-day discrepancy between the solar year (365 days) and the lunar year (29.5 × 12 = 354), lunar calendar dates are not tied to the seasons. If a certain day occurs this year in the spring, in a few years it will regress to the winter, and so on.

On the Jewish calendar, referred to as a lunisolar calendar, the dates are aligned with the seasons. For example, Passover must be celebrated in the spring. In order to prevent a regression, every two or three years a thirteenth month is added (more on that below).

Read: Introduction to the Jewish Calendar

5. The Names of the Months Came from Babylonia

Scripture generally describes the months based on their place in the calendar—e.g., third month, fourth month, and so on. The Hebrew names of the months as we know them today were brought to Israel from Babylonia at the onset of the second Jewish commonwealth, approximately 350 BCE.

Original source can be found here.