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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, e.g. at the end of Shabbat, when the prohibition of creative activities (melacha) remains in force until nightfall.

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

With the exception of the Shabbat, the weekdays have no names.  They are simply numbered:

  1. alef yom rishon = "first day" = (Sunday)
  2. bet yom sheni = "second day" = (Monday)
  3. gimel yom sh'lishi = "third day" = (Tuesday)
  4. dalet yom revi'i = "fourth day" = (Wednesday)
  5. he yom chamishi = "fifth day" = (Thursday)
  6. vav yom shishi = "sixth day" = (Friday)

The week culminates in the seventh day, the Holy Shabbat (shabbat kodesh, abbreviated sh''q).


Months

The Jewish month is based on the lunar or synodic month, the time it takes for the moon to circle the earth.  Since the exact duration of 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 is chaser ('defective').  There are two months which 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 when two witnesses had actually 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 is the one in which the Exodus from Egypt occurred (Yetziat Mitzrayim; 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 (with the exception of Rosh Hashana, the Jewish New Year) is Rosh Chodesh (lit. 'head of the month', abbreviated r''ch) — 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, it is "regular" (kesidra); if both have 30 days, it is "complete" (sh'lema) or "excessive"; 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, i.e. one revolution of the earth around the sun, which corresponds to the cycle of the seasons.  If the Jewish calendar were based exclusively on the lunar year, Pesach (15 Nisan) would fall in the spring in one year, in the winter a few years later, then in the autumn, then in the summer and – after about 33 years – in the spring again.  But the Torah says that Pesach must be celebrated in the spring (be-chodesh ha-aviv, Shemot [Exodus] 13:4), and so the average length of the Jewish year must be adjusted to the solar year.  This is achieved by adding an entire month about 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: 5755/19 = 302 + 17/19.  (This is something that you can calculate online.)

The extra month in a leap year has 30 days, so that the year lasts for 383, 384 or 385 days.  It is added after the month of Sh'vat and is called Adar I, whereas the original Adar (of 29 days) becomes Adar II.  Purim, which is on 14 Adar, is celebrated in Adar II in a leap year.  Someone who was born in Adar of a common year will celebrate 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 this is the seventh month), in September or early October according to the Gregorian (civil) calendar.  Jewish years are counted from the Creation of the world.  To convert the Jewish year to the year of the Common Era (CE), 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; the beginning of 5678 was in 1917.  When the year is written with Hebrew letters, the 5000 is usually omitted ("small count", abbreviated lf''q).  In that case, one can find the civil equivalent by adding 1240.  For instance, the numerical values of the letters tet-shin-nun-vav add up to 756, short for 5756.  That is the Jewish year which corresponds to 1996 (756 + 1240 = 1996); to be precise, it lasts from the evening of 24 September 1995 until the evening of 13 September 1996.  (The numerical equivalent of a year written in Hebrew letters can be determined online.)


Holidays

All Jewish holidays, fast days, remembrance days etc. have a fixed date in the Jewish calendar.  Some of them are shifted to a different day if they fall on or just before the 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, Chanuka in the apocryphal Books of the Maccabees.

Chanukka (Festival of Lights)
If Kislev has 30 days: 25 Kislev - 2 Tevet
If Kislev has 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 the Shabbat (with the exception of Yom Kippur), fast days that fall on Shabbat are shifted.

Tzom Gedalya (assassination of the governor Gedaliah)
3 Tishri
If 3 Tishri falls on Shabbat, the fast is observed on 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 13 Adar falls on Shabbat, the fast is observed on Thursday (11 Adar)
Shiv'a Asar b'Tammuz (first breach in the walls of Jerusalem during the Babylonian siege)
17 Tammuz
If 17 Tammuz falls on Shabbat, the fast is observed on Sunday (18 Tammuz)
Tish'a b'Av (destruction of the Temple)
9 Av
If 9 Av falls on Shabbat, the fast is observed on 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 5 Iyyar falls on Friday or Shabbat, the celebrations are held on Thursday (4 or 3 Iyyar),
so as to avoid a desecration of Shabbat
Lag ba-Omer (33rd day in the Omer period)
18 Iyyar
Yom Yerushalayim (Jerusalem Day)
28 Iyyar


Further Information:

Books

  • Arthur Spier, The Comprehensive Hebrew Calendar, 3rd ed., Spring Valley, NY / Jerusalem: Feldheim 1986. 
    [Brief guide to the Jewish calendar and conversion tables for 5660-5860 / 1900-2100 with Shabbat readings].
  • R' Nathan Bushwick, Understanding the Jewish Calendar, New York / Jerusalem: Moznaim 1989. 
    [Easy to follow, with many examples, tables and diagrams; some references to halachic sources].
  • William Moses Feldman, Rabbinical Mathematics and Astronomy, 4th ed., New York: Sepher-Hermon 1991. 
    [1st ed. 1931; more technical, analyzes astronomical calculations in the Talmud and in Maimonides' Kiddush ha-chodesh].


Computer Programs

There are numerous calendar conversion programs available, including:

  • JCAL for the civil years 1583-3239 by Lester Penner. (Shareware; with Shabbat readings, a file explaining the Jewish calendar and conversion utilities that accept dates as command line parameters).
  • HebCal for the civil years 1600-2200 by Joseph Kohn. (Shareware; with halakhic times, Shabbat readings and holiday lists etc., prints monthly calendars).
  • Jewish Calendar Conversions in One Step, by Steve Morse.


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Copyright ©1996 Joachim Mugdan, All rights reserved.
Created 3 Feb 1996.  Revised 15 Dec 1997 / 19 Apr 1999 / 3 Apr 2003 / 15 Nov 2006 / 20 Oct 2011 WSB
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