The Jewish Calendar in Jubilees

In contrast to the lunar-solar calendar found in Rabbinic sources, Jubilees follows a solar calendar of 364 days per year, to which it refers as a “complete year” (שנה תמימה):

Now you command the Israelites to keep the years in this number—364 days. Then the year will be complete and it will not disturb its time from its days or from its festivals because everything will happen in harmony with their testimony. They will neither omit a day nor disturb a festival. (6:32)

A similar calendar has been discovered in some of the Dead Sea scrolls from Qumran. A 364-day calendar is useful from the perspective that the number of days in a year is divisible by 7 (52 weeks = 364 days). Every date in the calendar is therefore anchored to a specific day of the week, and does not change from year to year.

The Jubilees calendar is further divided into four quarters, each of which consists of 91 days (13 weeks of 7 days), and since this number is also divisible by 7, each date in the quarter falls out on set day of the week, without any shifts from quarter-to-quarter or year-to-year. Each quarter in the calendar begins on Wednesday, the day of the creation of the heavenly bodies relevant to time keeping (1:14-19). Every quarter throughout history is identical, consisting of two months of 30 days and third day of 31. The entire calendar is summarized in the following chart:

Since the calendar is fixed from the time of creation, there is no human involvement in the setting of time – it is divinely mandated for all of eternity. This stands in stark contrast to the rabbinic halacha as described e.g. in m. Rosh Hashanah, in which witnesses and the beit din,the rabbinic court, played an integral role in declaring the new month, and thus the length of the previous month. Similarly, various derashot (homilies) in rabbinic literature emphasize that the festivals were established based upon human control over the calendar.

Jubilees polemicizes against those Jewish groups who incorporate the moon into their calendrical calculations, leading to an annual shift of 10 days, the difference between a lunar-solar calendar (of 354 days) and the Jubilees year:

There will be people who carefully observe the moon with lunar observations because it is corrupt (with respect to) the seasons and is early from year to year by ten days. Therefore, years will come about for them when they will disturb (the year) and make a day of testimony something worthless and a profane day a festival. Everyone will join together both holy days with the profane and the profane day with the holy day, for they will err regarding the months, the sabbaths, the festivals, and the jubilee. (6:36–37)

The caustic language in Jubilees reflects the intense debates between Jewish groups surrounding the calendar in antiquity, which also comes to the fore in rabbinic literature.^[1]

The Mishnah in Menachot (10:3) describes in detail the wave-offering ceremony that took place in the late Second Temple period, including an explicit reference to its polemical nature:

What was the procedure? The messengers of the Beth Din used to go out on the day before the festival and tie the unreaped corn in bunches to make it the easier to reap. All the inhabitants of the towns near by assembled there, so that it might be reaped with much display. As soon as it became dark, he called out, “Has the sun set?” And they answered, “Yes”. “Has the sun set?” And they answered, “Yes”. “With this sickle?” And they answered “Yes”. “With this sickle?” And they answered “Yes”. “Into this basket?” And they answered “Yes”. “Into this basket?” And they answered “Yes”. On the Sabbath he called out further, “On this Sabbath?” And they answered “Yes”. “On this Sabbath?” And they answered “Yes”. “Shall I reap?” And they answered “Reap”. “Shall I reap?” And they answered “Reap”. He repeated every matter three times, and they answered, “Yes.” “Yes.” “Yes.” And why was all this? Because of the Boethusians who maintained that the reaping of the Omer was not to take place at the conclusion of the [first day of the] festival. (my emphasis)

The ceremony described here was designed to draw attention, and thus to promote the position that the wave offering took place on the second day of the festival. This was no mere academic dispute, since there were very practical implications for the decision made, perhaps most importantly the date of Shavuot seven weeks later.

The polemical overtones in these two sources, Jubilees and the Mishnah, reflect the opposing views of competing groups, and demonstrates the intense arguments surrounding the calendar and the entire conception of the source of marking time, between Jews in antiquity.  Given that calendar is a major marker of religious identity, these debates were not merely academic, but had far-reaching implications, forcing Jews to mark their affiliation with one group or another by celebrating particular festivals according to that group’s calendar.