Question: "What is the structure of the Jewish calendar?"
Answer: The Jewish calendar is based on the lunar month, which is a bit longer than 29 ˝ days. As such, the Jewish lunar months are 29 or 30 days long. Twelve lunar months usually amount to 354 days, 11 days short of a solar year. In order for the festivals to stay in the correct season in relation to the solar year, an extra month is added every few years. The Jewish calendar is dated from what is supposed to have been the Creation: 3,760 years and three months before the Christian era. For that reason, to find the current year in the Jewish calendar, one must add 3,759 to the date in the Gregorian calendar. The system, however, will not work to the exact month, since the Jewish year (running on the civil calendar) begins in autumn rather than in midwinter. A Hebrew month begins in the middle of a month on our calendar today. Crops were planted in November and December and harvested in March and April.
1 Nisan (Abib)
2 lyyar (Ziv)
7 Tishri (Ethanim)
8 Marcheshvan (Bui)
1 Kings 6:1, 37
1 Kings 8:2
1 Kings 6:38
Since the Jewish month invariably began with the new moon, at intervals of approximately 29˝ days, the Jewish year ran 354 days. Late in Israel’s history, an extra month was inserted between Adar and Nisan. That month, sometimes called Veader (“second Adar”), was added seven times within a 19-year cycle (at which time Adar received an extra half day).
The names for the Jewish months as now known come from the period following the return from Babylonia to Palestine. Before the Babylonian exile, at least four other names were in use: Abib (Exodus 13:4), Ziv (1 Kings 6:1, 37), Ethanim ( 1 Kings 8:2), and Bul (1 Kings 6:38). After the Captivity, they were renamed Nisan, lyyar, Tishri, and Heshvan (originally Marcheshvan), respectively. The pre-exilic names carried agricultural connotations. For example, Abib signified the month in which the heads of the grain became ripe; Ziv was the month for desert flowers to bloom. An agricultural orientation is apparent in what is evidently the oldest Hebrew calendar, found at Gezer (southeast of Tel Aviv) in 1908 and dating from the 10th century BC. The calendar breaks down the year by agricultural activities such as sowing, reaping, pruning, and storage.
Primarily, however, the months were religiously significant to the Jews and enabled them to commemorate the important events of their history. Each month’s beginning was considered holy. To ancient Israel, the moon became a spiritual symbol of the nation itself; the sun eventually became symbolic of the Messiah (Malachi 4:2). Since the moon produces no light of its own, the symbolism is especially appropriate: Israel was supposed to reflect the Messiah’s light to the world.
The Jewish calendar remained unchanged during the period between the Old Testament and New Testament (approximately 400 years), despite an attempt by Hellenistic rulers to introduce a modified lunar-month system, presumably of Macedonian origin. According to that calendar, five days were added to the final month of the year, with each of the 12 months containing 30 days. Even then, it only approximated the solar year.
We know of no era in which the ancient Hebrews recorded dates by citing a month and day. Rather, dates were computed by reference to some significant event such as the accession year of the reigning king. In New Testament times, the Jews continued the Old Testament method of dating events by synchronizing them with events either in their religious calendar or within the secular sphere of the Roman world. Writers of the New Testament followed the same principle (Luke 1:5; John 12:1; Acts 18:12). It was only as the calendar reforms of Julius Caesar became embedded in the culture that people changed from that long-standing method to a more standardized system.