Mishnah Day
Subscribe | Donate December 14, 2010 | 7 Tevet 5771 | Week 370, Day 2

The Jewish Calendar—And Reform Options-Part One
Rabbi Richard Sarason

The Jewish calendar in use today is a rabbinic elaboration of the biblical calendar.  That calendar is lunisolar.  While the months are determined by the cycles of the moon (and particularly by the appearance of the new moon), the year is determined by the cycle of the sun.1 Specifically, Pesach must fall out each year in the spring, so the year is intercalated (that is, extra days are added) before the month of Nisan in which Pesach occurs.2

The lunar month—astronomically speaking, the period between one conjunction of the moon with the sun (during which the moon is not visible) and the next—is twenty-nine days plus a remainder (12 hours, 44 minutes, and 3 ½ seconds).  Since only full days are counted in the calendar, this means that some months in the Jewish year will have 30 days (Nisan, Sivan, Av, Tishrei, Shevat, Adar [1]), while the rest will have 29 (Iyar, Tammuz, Elul, Tevet, Adar [2]). The months of Marcheshvan and Kislev can vary in this regard from year to year.
Because the orbit of the earth around the sun is elliptical rather than circular, the exact length of the solar year is 365 days plus a remainder (5 hours, 48 minutes and 46 seconds).  Since the solar year is about 11 days longer than the lunar year, an additional month (Adar 2) is added in each of seven out of the nineteen years that constitute the lunar cycle. While some of the mathematical principles and calculations involved in the periodic intercalation of the calendar were already worked out by the Rabbis of the Talmud, the full regularization of the Jewish calendar, as we know it today, did not take place until the tenth century.3

The festivals of the Jewish year are all agricultural in origin; they are tied to the phases of the sun.  The vernal equinox4 marks the beginning of spring.  In the land of Israel, this is the end of the rainy season and the period of the wheat and barley harvests as well as the birthing season for flocks and herds.  The spring festival cycle begins with Pesach, at the full moon of the spring month (Nisan 15).  Agriculturally speaking, Pesach celebrates the new grain crop (hence the requirement to remove anything leavened—fermented—in order to begin the year with new, unsullied grain produce) as well as the new life among domesticated animals.  The first sheaf (‘omer) of the grain and the firstborn of the flocks and herds are offered up to God, who owns the land and governs its fertility, as an act of gratitude and in order to insure future fertility.  Barley matures approximately seven weeks later than wheat---so seven weeks are counted before bringing in the barley harvest and other first fruits of the crops (Shavu’ot).

The autumnal equinox5  marks the beginning of autumn.  In the land of Israel, this is the beginning of the rainy season and the time of harvest for late summer crops.  The festival of Sukkot, which begins at the full moon of the biblical seventh month (rabbinic first month) is the time of ingathering, when the rains are eagerly anticipated and fervently prayed for. Booths are put up in the fields so that the harvesters may stay out with the crops. The priestly festival calendars of Leviticus 23 and Numbers 28-29 also mark out the first and tenth days of the (biblical) seventh month for ritual attention.  The first day of the month is the time for blowing loud blasts (teru’ot), presumably in order to call God’s attention to the plight of the Israelite people, whose lives and livelihoods depend at this time of year on adequate rainfall and an abundant harvest.  The tenth day of the month is when the sanctuary must be purged of all impurities—and the people purified from their sins that defile the land and the sanctuary—in advance of the harvest ingathering and the onset of the rains.

Already in the biblical literature, these agricultural festivals come to be interpreted with reference to primal events in the mythic history of Israel. Pesach is identified with the archetypal redemption of Israel from Egypt:  the requirement to eat only new, unleavened bread is explained in terms of the Exodus narrative (the Israelites left Egypt in such haste that they had no time to let their dough leaven), as is the offering to God of the firstborn among the flocks and herds and the redemption of the firstborn sons (God struck down all the firstborn Egyptian males in the tenth plague).  Sukkot, too, is tied to the Exodus narrative (the festival booths are a reminder of the booths our ancestors inhabited on their journey through the wilderness after leaving Egypt).  Shavuot, on the other hand, is first identified in rabbinic literature as the time of the giving of the Torah at Sinai.

The winter solstice is marked by the lighting of lights during Hanukkah.  The summer solstice is no longer marked on the Jewish festival calendar (although Ezekiel 8:14 refers disparagingly to the women’s rite of weeping for Tammuz, the Babylonian fertility god, as vegetation died in the intense midsummer heat).  Instead, fasts connected with the destruction of the Temple (17th of Tammuz, 9th of Av) are observed.

The major seasonal festivals of spring (Pesach) and fall (Sukkot) each last a week, with an eighth-day concluding festival (called by the Rabbis, Shemini Atzeret) at the end of Sukkot.  Hanukkah, too, lasts eight days (it is modeled in this regard after Sukkot).  Shavuot, on the other hand, is observed for a single day, as are Rosh Hashanah and Yom Kippur.  In the Babylonian Diaspora, certainly by the time of the Talmud, it became customary to add an additional day to the observance of all of the biblical festivals (except, of course, for the fast of Yom Kippur, so as not to cause undue physical distress).  The reason for this two- day observance was that the beginning of each festival was set in the land of Israel and proclaimed by the rabbinical courts in the land.  It could take as long as a second day for the proclamation to be received in Babylonia---so a second day was observed as a precautionary measure (one of the two days observed was certainly the festival day).  By the time that the calendar came to be set according to foolproof mathematical calculations rather than fallible empirical astronomical observation, the second-day observance (yom tov sheni shel galuyyot) had become a longstanding and hallowed custom in Babylonia (and the Mediterranean diaspora under its influence)—and thus the custom was retained.  In the land of Israel only a single festival day was observed, and that remains customary today in the State of Israel. 

The custom of observing two days of Rosh Hashanah has a different basis that obtains even in the land of Israel: namely, doubt as to when the new moon of Tishrei actually occurs—particularly when this was dependent on the testimony of eyewitnesses.  The theoretical possibility of observing two days of Rosh Hashanah for this reason is raised in the Mishnah (Rosh Hashanah 4:4),6 but the list of festival Torah readings given at Mishnah Megillah 3:5 and Tosefta Megillah 3:6 suggests that, in fact, the mishnaic custom was to observe only a single day of Rosh Hashanah (no reading is listed in either Mishnah or Tosefta for a second day of Rosh Hashanah).  The present custom of observing two days of Rosh Hashanah in the land of Israel as well dates from the twelfth century, when Jews from Provence settled there and instituted the custom.

Dr. Sarason is Professor of Rabbinic Literature and Thought and the Associate Editor of the Hebrew Union College Annual. He was ordained at HUC-JIR.

1. By contrast, the Islamic calendar is fully lunar—that is why the major, month-long observance of Ramadan travels around the solar calendar, never at the same solar time each year.  The Gregorian calendar in use in western countries is a solar calendar—that is why the holidays of the Jewish year can fall out on it with as much as a month’s variance over a period of several years.  A 364-day schematic solar calendar was used by the Jewish sectarians at Qumran during the late Second Temple period.  It is attested in the calendrical scrolls found there.  This calendar is also known from the Enochic Astronomical Book (1 Enoch 72-82) and the Book of Jubilees, both texts from the late Second Temple period.  See the article, “Calendars,” in John J. Collins and Daniel C. Harlow, The Eerdmans Dictionary of Early Judaism (Grand Rapids, MI: William B. Eerdmans, 2010) 457-460.

2. The names of the Hebrew months in use today—Tishrei, Marcheshvan, Kislev, etc.—are actually Babylonian.  The old Hebrew/Canaanite names are found in the older sections of the biblical narrative—Aviv, Bul, Ziv, Eitanim (only these four are mentioned by name).  Before the Babylonian exile, the Hebrew year began in the spring (cf. Ex. 12:1---“This month [Aviv, during which Pesach falls] shall mark for you the beginning of the months; it shall be the first of the months of the year for you”).  The Babylonian year began in the fall—this custom is preserved in the post-exilic and rabbinic calendars.  In the rabbinic calendar, Rosh Hashanah, the beginning of the year, is the first day of Tishrei---while in the biblical calendar, this day, referred to as the day of loud blasts (yom teru’ah; zikhron teru’ah) falls on the first day of the seventh month, seven months after Aviv.

3. For a fuller account, see the article “Calendar,” in the Encyclopaedia Judaica (Jerusalem: Keter, 1971) 5:43ff.

4. The vernal equinox is the point at which days and nights are the same length while the days are getting longer.

5. The autumnal equinox is the point at which days and nights are the same length, while the days are getting shorter.

6. But the situation envisaged here, during Temple times, is quite specific.  See the discussion on this entire issue by Charles L. Arian and Clifford E. Librach, “The ‘Second Day’ of Rosh Hashanah:  History, Law, and Practice,” in Journal of Reform Judaism [=CCAR Journal] 32:3, Summer, 1985, 7-83.

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