The Jewish calendar (Numbers 29)

Most people groups of the ancient world calculated months by the cycles of the moon; each new moon marked the beginning of a new month. However, the moon completes one revolution around the earth in only about 29,5 days. So the lunar year of 12 lunar months is only 354 days long – somewhat shorter than the solar year of 365,25 days. During a period of a few years the months would begin to misalign with their associated seasons on a lunar calendar. This phenomenon no doubt caused great confusion and consternation in matters such as setting a schedule of annual festivals or creating an agricultural calendar.

The Babylonians periodically added intercalary days (days inserted into a calendar) to the year in order to realign the solar and lunar years. The Assyrians, however, allowed the lunar months to fall behind the solar year until finally adopting the Babylonian system during the reign of Tiglath-Pileser III. The Egyptians did not follow a lunar year but divided the year into 12 equal months, each with 30 days, ans added 5 extra days at the end of each year. The Jewish calendar, which was similar to its Babylonian counterpart, derived the names of the months from the Babylonian names.

The first month of the Jewish calendar, Nisan, corresponds to the Canaanite Abib. These names sometimes appear in the Bible (e.g. Nehemiah 2:1, Esther 8:9, Zecheriah 1:7), although most months mentioned there are simply designated by number (e.g. “the eleventh month”). A thirteenth month is added in 7 of every 19 years to keep the calendar synchronized with the agricultural seasons.

Some confusion exists about whether the Israelites began their calendar year in the spring or in the fall. The first day of the seventh month (Tishri) is designated for the Feast of Trumpets (Numbers 29:1), and the same date eventually became fixed as the day of the Jewish New Year (Rosh Hashanah). This suggests an autumnal new year. However, most evidence points to the spring being the season of the new year. Most significantly, Nisan, which begins in March and ends in April, is routinely called “the first month” in the Bible. Thus it appears that the Israelites began their calendar year in the sping but followed an agricultural year that went from autumn to autumn. The Gezer Calendar, for example, reflects the agricultural year. To explain this difference using a modern anaaogy, out calendar year begins on January 1, but many institutions and nations run a fiscal-year calendar that begins and ends on different dates.

Scholars also have differing opinions about whether the Israelites regarded evening or morning as the beginning of a new day. Most evidence implies that their day began in the evening (cf. Leviticus 23:32). The Israelites observed a seven-day week (Exodus 34:21; cf. the creation account in Genesis 1:1-2:3), and the Roman Empire officially adopted the seven-day week during the reign of Constantine in A.D. 321.

The matter of enumerating years during ancient times sometimes caused great confusion because there was no universally accepted, fixed point for the beginning of “Year One”. The Romans counted their years from the commonly accepted date of the founding of Rome, but ancient Israel, like most other Near Eastern nations, numbered years according to the reign of kings (e.g. “in the second year of king X”), which, of course, overlapped and varied in terms of duration. The difficulties with such a system were aggravated by the fact that a king’s “first year” could be either the year during which he became king or the first full year of his reign after “New Year’s Day”.

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