The Jewish calendar is primarily lunar, with each month beginning on the new moon. An ordinary (non-leap) year has 12 months and about 354 days. Since 12 months are about 11 days shorter than a solar year, a leap month is added about every 3 years to keep the calendar in tune with the seasons. The first month of the religious calendar is the month of Nisan. But the Jewish civil New Year is in Tishri, the seventh month.
The 12 months of an ordinary year totaled to 353, 354, or 355 days. A leap year has 383, 384, or 385 days. The three lengths of the years are called deficient, regular, and complete, respectively. The Jewish calendar now has complex rules to determine the length of a year (visit http://webexhibits.org/calendars/calendar-jewish.html for more information). But in ancient times, the beginning of a month was determined by observation. When people observed the new moon, they would notify the Sanhedrin (an assembly of religious leaders). When the Sanhedrin heard testimony from two independent, reliable eyewitnesses that the new moon had occurred, they would declare the beginning of a new month and send out messengers to tell people when the month began.
In the Torah (the first five books of Moses), there were seven sacred festivals instituted by God:
Of the above, three were considered as "major feasts": the Feast of Passover (Pesach), the Feast of Weeks (Pentecost), and the Feast of Tabernacles (Sukkot). These are often called "pilgrim feasts" because all adult males were required to travel to the sanctuary to take part (Deuteronomy 16:16).
At a much later time two more civil holidays were introduced:
In addition to the above festivals, the followings were to be observed:
The following table summarizes the Jewish calendar and the sacred festivals. All Jewish holidays begin the evening before the date specified. This is because a Jewish day begins and ends at sunset, rather than at midnight.
Jewish Calendar
Length in a
deficient yearLength in a
regular yearLength in a
complete yearFestivals and Holidays
Gregorian Calendar
1
NISAN30 30 30 14 evening. Passover (Pesach)
15-21. The Feast of Unleavened BreadMarch April 2
IYAR29 29 29 14. Second Passover (Pesach Sheni) May 3
SIVAN30 30 30 6. Weeks (Shavuot) June 4
TAMMUZ29 29 29 July 5
AV30 30 30 August 6
ELUL29 29 29 September 7
TISHRI30 30 30 1. Trumpets (Yom Teruah)
10. The Day of Atonement (Yom Kippur)
15-21. Tabernacles (Sukkot)
22. Last Great Day (Shmini Atzeret)October 8
HESHVAN29 29 30 November 9
KISLEV29 30 30 25 - 2 Tevet. The Festival of Lights (Hanukkah) December 10
TEVET29 29 29 January 11
SHEVAT30 30 30 February 12
ADAR I*30
(leap year only)30
(leap year only)30
(leap year only)March 13
ADAR II29 29 29 14. Purim Total 353 or
383 (leap year)354 or
384 (leap year)355 or
385 (leap year)
* The month Adar I is present only in leap years. In an ordinary year, Adar II is simply called Adar.
The Five Offerings - Presents an overview of the sacrificial system.
Calendars through the Ages. "The Jewish calendar." http://webexhibits.org/calendars/calendar-jewish.html
Discovery Series. "The Holidays of God - The Spring Feasts." http://www.gospelcom.net/rbc/ds/q0407/
Discovery Series. "The Holidays of God - The Fall Feasts." http://www.gospelcom.net/rbc/ds/q0408/
The Wild Olive. "The Feast of The Lord and Jewish Feasts." http://fp.thebeers.f9.co.uk/feasts_of_the_lord.htm
Jewish 101. "Judaism 101: Jewish Calendar" http://www.jewfaq.org/calendar.htm