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What is the Purpose and History of Adar II?

 Volume 18, Number 3

March 2024

What is the Purpose and History of Adar II?

By Cantor Abe Golinkin and Rabbi David Golinkin

In memory of our teacher
Rabbi Avraham Baharan z”l (1935-1995)
who taught his students some of
the secrets of the Jewish calendar.

Rabbi Avraham Baharan z”l was a very dynamic and charismatic teacher who taught us at the Hebrew Academy of Washington from 1965-1968. He transmitted to his students an understanding of the Jewish Calendar, in a very clear and easy-to-comprehend manner. The initial version of the responsum was written by my brother Cantor Abe Golinkin as a way of passing on that important knowledge to as many Jews as possible, so that they will feel at home with our calendar. I then added sources, a section on the Babylonian calendar, and a bibliography. DG

 * * *

I. The Dilemma of the Jewish Calendar

The civil calendar is based on the solar year, which consists of one cycle of the earth around the sun. The Jewish calendar is lunisolar: the years follow the sun and the seasons of the year, while the months follow the lunar year, which consists of 12 cycles of the moon around Earth.

In the civil calendar, a solar year contains approximately 365.25 days, while in the Jewish calendar, a lunar year of 12 months contains approximately 354.33 days (Rambam 6:4; ET, Luah, notes 340-343).

What does the Jewish calendar do to deal with the fact that the lunar year falls behind the solar year by approximately 10 days, 21 hours each year (Rambam, ibid.)?

One option would be do nothing, to allow this pattern to persist, without any intervention — and let all of our holidays slide through the seasons. Indeed, this is what the Moslems do. They only follow the lunar calendar. The result is that Ramadan wanders through the seasons. In other words, Ramadan can occur at any season of the year and approximately every 33 years a given month passes through the entire cycle of seasons.

But our ancestors decided that they needed to keep the lunar calendar in sync with the seasons. Why?

The most popular explanation is that the Torah says “Observe the month of Aviv and make a Pesah [sacrifice] to the Lord your God” (Deut. 16:1). A number of important rabbinic sources (Mekhilta Bo, Parashah 2, ed. Horowitz-Rabin, p. 8; Rosh Hashanah 21a; Rambam 4:1; ET, Aviv, note 3) say that this verse is a command to add a month before Pesah in order to make sure that the Pesah sacrifice is offered in Aviv, the biblical name for the month of Nisan, i.e., in the Spring. Or, as the Rambam explains: “and why do they add [the month of Adar II]? So that the month of the Pesah sacrifice shall fall in the season of the Aviv… as it is written: ‘Observe the month of Aviv [and make a Pesah sacrifice to the Lord your God].’ If not for adding this month, Pesah would occur sometimes in the summer and sometimes in the rainy season.” Indeed, some of the rabbis who enumerated the 613 mitzvot considered this to be one of the positive commandments.

The connection between Pesah and the month of Aviv is also stressed in Exodus 13:4-5, 23:15, and 34:18. In fact, the sections of the Torah that include the instruction to celebrate Passover in Aviv were considered so important, that they are the designated Torah readings for many of the days of Pesah.

However, the Meiri (Provence, 1249-1316) has a broader approach. He stresses in his commentary to Rosh Hashanah 21a (ed. Sofer, p. 51) that we need to keep the lunar and solar years in sync “so that our Pesah will occur in the time of Aviv and our Sukkot in the time of Assif (ingathering).” In other words, if the calendar was not adjusted, all three of the agricultural festivals would sometimes fall in the wrong season. Shavuot, which is called Yom Habikkurim, the festival of First Fruits (Numbers 28:26), would occur at any season of the year, and Sukkot, which is called Hag Ha’asif, the festival of the ingathering of the crops (Exodus 23:16 and 34:22 and Rosh Hashanah 13a), would occur at any season of the year.

 II. The Solution — a Leap Month

While the civil calendar’s leap year only adds one day to the year, the Jewish leap year adds an extra month to our calendar. This is done, every 2-3 years, to compensate for the whole month our calendar falls behind the civil calendar in the course of 3 years – approximately 11 days per year X 3 years = 33 days (see Rambam 1:2).

We insert this leap month, a 13th month, into our calendar after Adar, which is the 12th month of the year (see Esther 3:7) and just before Nisan, which is the first month of the year (ibid.).

The Jewish leap month was not given a name of its own. Since the leap month is inserted after the month of Adar, it was decided that the leap month should be called Adar Sheni or Second Adar. Indeed, this term is mentioned in Mishnah Megillah 1:4 and Tosefta Megillah 1:6 (ed. Lieberman, p. 345).

This process of adding a month is called intercalation in English and Ibur Hashanah in Hebrew (Mishnah Megillah 1:4; Nedarim 8:5; Sanhedrin 1:2; Arakhin 9:3 and more).

III. Which Years Have a Leap Month?

Until the year 358-359 CE, there was no fixed calendar. The leap months were intercalated by the Nasi (Patriarch) and the Sanhedrin in order to keep the lunar and solar years in sync. The main rabbinic sources about Ibur Hashanah are found in Tosefta Sanhedrin, Chapter 2 (ed. Zuckermandel, pp. 416-418); Yerushalmi Sanhedrin, Chapter 1, fol. 18d; Bavli Sanhedrin 11a-12a; Bavli Rosh Hashanah 21a; and have been summarized by the Rambam 4:2-7, 17.

One Baraita (teaching of the Sages of the Mishnah) states that there are three main signs or reasons to intercalate a year: for the Aviv (see above), for the fruits of the trees, and for the Tekufah (that Pesah should fall in the Spring).

Another Baraita states that one may intercalate the year for the sake of fixing the roads and the bridges in order to enable the pilgrims to go up to Jerusalem, for the sake of the Pesah ovens which need to dry out in the sun before Pesah, and for the sake of the Exiles who are on the way to Jerusalem and have not yet arrived.

A third Baraita states that we do not intercalate the year for the sake of kids and lambs, in order to allow them to grow up sufficiently to be used for the Pesah sacrifice, or for the sake of pigeons to grow up to be used as sacrificial birds, but these three reasons can be used as a support to the three reasons mentioned above.

These Beraitot have even preserved two Aramaic letters from the Patriarchs Rabban Gamliel and Rabban Shimon ben Gamliel to the Jews of the Diaspora explaining that the Sanhedrin has decided to intercalate the year for the following reasons.

Finally, another passage in Sanhedrin (fol. 18b) relates that the Sages once overheard three shepherds discussing what weather is characteristic of Adar, and if that weather does not occur, it is not really Adar. As a result, the Sages intercalated the year and added Adar II.

However, in the fourth century, the political situation of the Jews in Eretz Yisrael deteriorated. Rav Hai Gaon (d. 1038) relates (ET, Luah, notes 31-32) that, as a result, in the year 358-359 CE, the Patriarch Hillel II fixed the Jewish calendar. More recent research based on the Cairo Genizah and other documents has revealed that the process of fixing the calendar actually lasted until ca. 840 CE (see Sar-Shalom). This fixing of the calendar is frequently called Sod Ha’ibbur, the secret of the intercalation (cf. Rambam 11:4 and ET, Luah, notes 7-8). This fixing of the calendar set in motion a system with a repeating pattern of leap years, that would essentially run on “auto-pilot” in perpetuity. It fixed the 19-year cycle, which is known in Hebrew as the Mahzor Kattan. This repeating pattern fine-tuned the calendar, with the insertion of 7 Jewish leap years every second or third year in each 19-year cycle. This is based on the notion that 235 lunar months are equal to 19 solar years (ET, Luah, note 345; and cf. Rambam 6:10-11 and 10:1).

The intercalated years in each 19-year cycle will always be: the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years of the cycle. Jews memorize these years via the Hebrew mnemonic: גו”ח אדז”ט.

For the purpose of orientation, the 1st year of the current 19-year cycle was 5777 (2016-2017). We are now in 5784 (2023-2024), which is the 8th year of the 19-year cycle. That is why this year is a Jewish leap year.

Based on the repeating pattern above, the next four Jewish leap years in the current 19-year cycle will be:

Year 11 – 5787 (2026 – 2027);
Year 14 – 5790 (2029 – 2030);
Year 17 – 5793 (2032 – 2033);
Year 19 – 5795 (2034 – 2035).

IV. The Babylonian Origins of the Jewish Calendar

In the Bible, the months are frequently mentioned by number and not by name (e.g., Zekhariah 7:3-4 and 8:19). However, four months are mentioned by their Canaanite names in the earlier books of the Bible:

Aviv, the first month: Exodus 13:4-5; 23:15; 34:18; Deut. 16:1;
Ziv, the second month: I Kings 6:1, 37;
Eitanim, the seventh month: I Kings 8:2;
Bul, the eighth month: I Kings 6:38.

When the Jews returned to Eretz Yisrael from the Babylonian Exile beginning in 516 BCE, they brought back with them the Babylonian calendar which included the names of the months, and the 19-year cycle for intercalating the year. Indeed, the first fact is stated explicitly in the Talmud Yerushalmi (Rosh Hashanah 1:2, fol. 56d): “For Rabbi Hanina said: They brought back with them from Babylonia the names of the months.”

Here are the names of the Babylonian months and their Hebrew equivalents, along with their occurrence in the later books of the Bible:

Nisannu – Nisan: Nehemiah 2:1; Esther 3:7
Ayaru  — Iyar
Simanu – Sivan (m = v in many Semitic languages): Esther 8:9
Du’uzu – Tamuz (this is the only month with a different name)
Abu – Av
Ululu – Elul: Nehemiah 6:15
Tashritu – Tishrei
Arahsamnu – Marheshvan (see below)
Kislimu – Kislev (m = v as above): Nehemiah 1:1; Zekhariah 7:1
Tebetu – Tevet: Esther 2:16
Shabatu – Shevat: Zekhariah 1:7
Addaru – Adar: Ezra 6:15 and eight times in the book of Esther.

Indeed, this chart helps explain the name of the month of Marheshvan. The standard homiletic explanation is that Heshvan is mar or bitter because it has no holidays. However, Moshe Kosovsky z”l, the very erudite author of the Concordance to the Talmud Yerushalmi, explained to me back in 1978 that Arahsamnu simply means “the eighth month.” Marheshvan is simply a metathesis of the Babylonian Arahsamna since the double vav and mem switch in Semitic languages. Indeed, this explanation was first suggested by both Norris and Schrader before 1877 (see Epstein).

However, the Jewish people did not adopt the Babylonian calendar as is. Thus, for example, in the Babylonian 19-year cycle, most of the leap years add a second Adaru, but in the 17th year of the cycle, they add a second Ululu. This difference is hinted at in a cryptic passage in the tractate of Rosh Hashanah fol. 32a (and parallels), which I explained back in 1988 (see Golinkin 1988). The Talmud states there in the name of Rabbi Hanina bar Kahana: “From the days of Ezra and onward we have not found Elul to be intercalated.” The standard explanation is that the month of Elul must always be a “defective month” of 29 days and not a “full month” of 30 days. However, following a suggestion made by Ben Zion Wacholder and David Weisberg in 1971, I think that the original meaning of this sentence was that from the days of Ezra we do not add Elul II in a leap year! Indeed, they also cite Sanhedrin 12a where a Baraita states that “One does not intercalate the year before Rosh Hashanah (i.e., in Elul)… and even so, we only intercalate Adar.” In other words, even though we adopted the Babylonian calendar and add 7 leap years in every 19-year cycle, we only add Adar II — and not Elul II like the Babylonians.

Some may find all of this surprising. How could we have borrowed our calendar from the Babylonians!? To this I would reply that the Jewish people have never lived in a vacuum. We have always borrowed and adjusted laws and customs from other peoples. As I have shown elsewhere (Golinkin 2006), the most famous example is that of the Pesah Seder which we borrowed from the Greek/Roman Symposium. The form remained the same, but the contents were totally transformed. And so it is with our calendar. We adopted the Babylonian lunisolar calendar in order to make sure that Pesah fell in the spring, Shavuot at the time of first fruits, and Sukkot at harvest time. We also adopted the names of the months. But when Hillel II saw that the Sanhedrin could no longer intercalate the year, he fixed the 19-year cycle of leap years based on, but not identical to, the Babylonian model.

V. Conclusion: The Hope

The perpetual Jewish calendar launched by Hillel II in 358-359 CE has helped to keep our dispersed people united, for the past 1666 years. May it continue to do so, in perpetuity!

Abe Golinkin and David Golinkin
Columbia, Maryland and Jerusalem
18 Adar II, 5784



1. Codes of Jewish Law

 Rambam — Rambam, Hilkhot Kiddush Hahodesh

2. Literature *

Anchor – The Anchor Bible Dictionary, Vol. 1, New York, 1992, pp. 810-820, s.v. Calendars

BritannicaThe New Encyclopaedia Britannica, 15th edition, Macropedia, Volume 3, Chicago, 1979, pp. 599-612, s.v. Calendar

Eisenstein – J. D. Eisenstein, Otzar Yisrael, Vol. 7, New York, 1907-1913, pp. 306-311, s.v. Ibbur Shanim

EJ – Encyclopaedia Judiaca, Vol. 5, cols. 43-53 = second edition, Vol. 4, pp. 354-359, s.v. Calendar  

Epstein – Avraham Epstein, “Marheshvan/Arah-Shamna”, Mikadmoniot Hayehudim, second edition, Jerusalem, 1965, pp. 22-28 (Hebrew)

ET, Aviv — Entziklopedia Talmudit, Vol. 1, 1973, cols. 52-55, s.v. Aviv

ET, Luah — Entziklopedia Talmudit, Vol. 36, 2016, cols. 75 ff., s.v. Luah Hashanah

Golinkin 1988 — Perek Yom Tov Shel Rosh Hashanah…, PhD dissertation, JTS, New York, 1988, pp. 59-60

Golinkin 2006 – “The Origins of the Seder”, Insight Israel: The View from Schechter, second series, Jerusalem, 2006, Chapter Nine, pp. 68-76

JE – The Jewish Encyclopedia, Vol. III, New York, 1902, pp. 498-508, s.v. Calendar, History of; Calendar

Pietruszka – Symcha Pietruszka, Yiddishe Folks-Entziklopedia, Vol. 2, Montreal, 1943, cols. 656-659, s.v. Calendar (Yiddish)

Sar-Shalom – Rahamim Sar-Shalom, “When was the Hebrew calendar founded?”, Sinai 102 (5748), pp. 26-51 (Hebrew)

Segal – J. B. Segal, Entziklopedia Mikrait, Vol. 8, cols. 203-209, s.v. Shanah

Spier – Arthur Spier, The Comprehensive Hebrew Calendar, third edition, New York, 1986

Wacholder and Weisberg – Ben Zion Wacholder and David Weisberg, “Visibility of the New Moon in Cuneiform and Rabbinic Sources”, HUCA 42 (1971), pp. 237-238

* There is a vast literature devoted to the Jewish calendar. One can find many of the sources and books by consulting the above articles.


To Purchase Rabbi Golinkin’s Volumes of Responsa: CLICK HERE

David Golinkin is President of The Schechter Institutes, Inc. and President Emeritus of the Schechter Institute of Jewish Studies. For twenty years he served as Chair of the Va’ad Halakhah (Law Committee) of the Rabbinical Assembly which gives halakhic guidance to the Masorti Movement in Israel. He is the founder and director of the Institute of Applied Halakhah at Schechter and also directs the Center for Women in Jewish Law. Rabbi Professor Golinkin made aliyah in 1972, earning a BA in Jewish History and two teaching certificates from The Hebrew University in Jerusalem. He received an MA in Rabbinics and a PhD in Talmud from the Jewish Theological Seminary of America where he was also ordained as Rabbi. For a complete bio click here.

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