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About the Jewish Calendar

Introduction to the Jewish Calendar

Days and Weeks

The Jewish day begins at sunset. The status of the period between sunset (the disappearance of the sun behind the horizon) and nightfall (the emergence of three medium-sized stars) is doubtful. For some purposes it is treated as part of the previous day — for example at the end of Shabbat, when the prohibition of creative activities (melacha) remains in force until nightfall.

Books and computer programs for conversion between the Jewish and Gregorian (civil) calendars are based on the daylight portion of the Jewish day. For instance, if you know that an ancestor was born on 26 Nisan 5580, you will find that this corresponds to 10 April 1820 — but the actual birthday may have been the previous evening, 9 April 1820.

With the exception of Shabbat, the weekdays have no names; they are simply numbered:

1. א — yom rishon = “first day” (Sunday)
2. ב — yom sheni = “second day” (Monday)
3. ג — yom sh'lishi = “third day” (Tuesday)
4. ד — yom revi'i = “fourth day” (Wednesday)
5. ה — yom chamishi = “fifth day” (Thursday)
6. ו — yom shishi = “sixth day” (Friday)

The week culminates in the seventh day, the Holy Shabbat (shabbat kodesh).

Months

The Jewish month is based on the lunar (synodic) month, the time it takes for the moon to circle the earth. Since one revolution is a little over 29.5 days, the length of the months normally alternates between 29 and 30 days. A month of 30 days is called male (“full”), one of 29 days chaser (“defective”). Two months are male in some years and chaser in others.

The month begins with the appearance of the new moon. In the time of the Temple, the Sanhedrin (the highest court) sanctified the new month once two witnesses had sighted the moon. In the middle of the fourth century C.E., a fixed calendar was introduced.

In the Torah the months are numbered, the first being the one in which the Exodus from Egypt occurred (cf. Shemot [Exodus] 12:2). Later, names of Babylonian origin were adopted:

1. ניסן — Nisan — (30 days)
2. אייר — Iyyar — (29 days)
3. סיון — Sivan — (30 days)
4. תמוז — Tammuz — (29 days)
5. אב — Av — (30 days)
6. אלול — Elul — (29 days)
7. תשרי — Tishri — (30 days)
8. חשון — Cheshvan — (29 or 30 days)
9. כסלו — Kislev — (30 or 29 days)
10. טבת — Tevet — (29 days)
11. שבט — Sh'vat — (30 days)
12. אדר — Adar — (29 days)

The first day of each month (except Rosh Hashana, the Jewish New Year) is Rosh Chodesh (“head of the month”) — and so is the thirtieth day of the preceding month, if there is one. For example, if a gravestone inscription mentions the first day of Rosh Chodesh Elul, the calendar date “30 Av” is meant.

Years

An ordinary year consists of twelve months. When Cheshvan has 29 days and Kislev 30, the year is “regular” (kesidra); if both have 30 days it is “complete” (sh'lema); and if both have 29 days it is “defective” (chasera). Thus an ordinary year can have 353, 354, or 355 days.

A lunar year of 354 days is about 11 days shorter than the solar year. If the Jewish calendar were based exclusively on the lunar year, Pesach (15 Nisan) would drift through the seasons, returning to spring only after about 33 years. But the Torah requires that Pesach be celebrated in the spring (cf. Shemot [Exodus] 13:4), so the average length of the Jewish year is adjusted to the solar year by adding an entire month roughly every three years. In each cycle of 19 years, the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years are leap years; the others are common years. For example, 5755 was a leap year because it was the 17th year in the 303rd cycle of 19 years. (You can check this with the Hebrew Year Converter.)

The extra month in a leap year has 30 days, so the year lasts 383, 384, or 385 days. It is added after Sh'vat and called Adar I, while the original Adar (29 days) becomes Adar II. Purim, on 14 Adar, is celebrated in Adar II in a leap year. Someone born in Adar of a common year celebrates the anniversary in Adar II in leap years, but yahrzeit for someone who died in Adar of a common year is observed in Adar I in leap years.

The new year begins with Rosh Hashana, the first of Tishri (although Tishri is the seventh month), in September or early October by the civil calendar. Jewish years are counted from the Creation of the world. To convert a Jewish year to the Common Era, subtract 3760 (or 3761 for the first months; in most years, 1 January falls in Tevet). For example, the major part of the Jewish year 5678 corresponded to 1918, and the beginning of 5678 was in 1917. When the year is written with Hebrew letters, the 5000 is usually omitted (the “small count”); in that case the civil equivalent is found by adding 1240. For instance, the letters טשנו add up to 756, short for 5756 — the Jewish year corresponding to 1996 (756 + 1240). (The numerical value of a year written in Hebrew letters can be determined with the Hebrew Year Converter.)

Holidays

All Jewish holidays, fast days, and remembrance days have a fixed date in the Jewish calendar. Some are shifted to a different day if they fall on or just before Shabbat.

Major festivals

The Torah describes two cycles of festivals (cf. Vayikra [Leviticus] Ch. 23, Bamidbar [Numbers] Ch. 28–29): the three pilgrimage festivals (Pesach, Shavuot, Sukkot) and the High Holidays (Rosh Hashana, Yom Kippur).

Rosh Hashana (New Year)

1–2 Tishri

Yom Kippur (Day of Atonement)

10 Tishri

Sukkot (Tabernacles): Full Holiday

Diaspora: 15–16 Tishri; Israel: 15 Tishri

Sukkot: Chol Hamoed (Semi-Holidays)

Diaspora: 17–21 Tishri; Israel: 16–21 Tishri

Sh'mini Atzeret (Eighth Day of Assembly)

22 Tishri

Simchat Tora (Rejoicing of the Tora)

Diaspora: 23 Tishri; Israel: combined with Sh'mini Atzeret (22 Tishri)

Pesach (Passover): Full Holiday

Diaspora: 15–16 Nisan; Israel: 15 Nisan

Pesach: Chol Hamoed (Semi-Holidays)

Diaspora: 17–20 Nisan; Israel: 16–20 Nisan

Pesach: Final Holiday

Diaspora: 21–22 Nisan; Israel: 21 Nisan

Shavuot (Festival of Weeks)

Diaspora: 6–7 Sivan; Israel: 6 Sivan

Minor festivals

Two festivals commemorating the miraculous salvation of the Jewish people were instituted after the beginning of the Babylonian exile: Purim has its basis in the biblical Book of Esther, Chanukka in the apocryphal Books of the Maccabees.

Chanukka (Festival of Lights)

If Kislev has 30 days: 25 Kislev – 2 Tevet; if 29 days: 25 Kislev – 3 Tevet

Purim (Festival of Lots)

14 Adar (in leap years Adar II); Shushan Purim in Jerusalem: 15 Adar (in leap years Adar II)

Fast days

In addition to Yom Kippur and Ta'anit Esther, four public fast days commemorating the destruction of the first Temple were instituted in the era of the Prophets (cf. Zechariah 8:19). Since fasting is forbidden on Shabbat (except Yom Kippur), fast days that fall on Shabbat are shifted.

Tzom Gedalya (assassination of the governor Gedaliah)

3 Tishri (if on Shabbat, observed Sunday, 4 Tishri)

Asara b'Tevet (beginning of the Babylonian siege of Jerusalem)

10 Tevet

Ta'anit Ester (Fast of Esther)

13 Adar (in leap years Adar II); if on Shabbat, observed Thursday (11 Adar)

Shiv'a Asar b'Tammuz (first breach in the walls of Jerusalem)

17 Tammuz (if on Shabbat, observed Sunday, 18 Tammuz)

Tish'a b'Av (destruction of the Temple)

9 Av (if on Shabbat, observed Sunday, 10 Av)

Other special days

After the proclamation of the State of Israel, new minor festivals and memorial days were introduced; Tu bi-Shvat and Lag ba-Omer, which go back to Talmudic times, became particularly popular with children.

Tu bi-Shvat (New Year of Trees)

15 Sh'vat

Yom ha-Sho'ah (Holocaust Memorial Day)

27 Nisan

Yom ha-Zikkaron (Memorial Day for fallen Israeli soldiers)

Eve of Yom ha-Atzma'ut

Yom ha-Atzma'ut (Israel Independence Day)

5 Iyyar (if on Friday or Shabbat, celebrations held Thursday, 4 or 3 Iyyar, to avoid desecrating Shabbat)

Lag ba-Omer (33rd day in the Omer period)

18 Iyyar

Yom Yerushalayim (Jerusalem Day)

28 Iyyar

Books

• Arthur Spier, The Comprehensive Hebrew Calendar, 3rd ed., Spring Valley, NY / Jerusalem: Feldheim, 1986. A brief guide with conversion tables for 5660–5860 / 1900–2100 and Shabbat readings.
• R' Nathan Bushwick, Understanding the Jewish Calendar, New York / Jerusalem: Moznaim, 1989. Easy to follow, with many examples, tables, and diagrams.
• William Moses Feldman, Rabbinical Mathematics and Astronomy, 4th ed., New York: Sepher-Hermon, 1991. More technical; analyzes astronomical calculations in the Talmud and in Maimonides' Kiddush ha-chodesh.

Computer Programs

• HebCal for the civil years 1600–2200, with halakhic times, Shabbat readings, and holiday lists.
• Jewish Calendar Conversions in One Step, by Steve Morse.

Related JewishGen Tools

• Hebrew Year Converter — Hebrew letters / numerals and leap-year check.
• Calendar Converter — civil / Hebrew date conversion.
• Festival Dates — Jewish holidays for any year.

Copyright ©1996 Joachim Mugdan, all rights reserved. Adapted from the JewishGen InfoFile “Introduction to the Jewish Calendar.”