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QUESTION: I have a few questions regarding the Jewish leap year. Why is Adar the month that is picked for this purpose? Why do we call it Adar Alef? Why is Purim celebrated in the second Adar? Which one of them is the real Adar?

Shea Aronovitch
(Via E-Mail)



ANSWER: We will answer your questions, however, not necessarily in the order that you have asked. First, we deal with the name Adar. The Gemara (Jerusalem Talmud, Rosh Hashanah 1:2) cites Rabbi Chanina who states, “The names of the [Jewish] months were brought up with them [the exiles who returned to the Land of Israel] from Babylonia.” Indeed, these were not the original names, as we see in the various biblical verses that refer to them only in a numerical fashion (as previously discussed in this column regarding the name of the eighth month – Marcheshvan).

The Gemara supports Rabbi Chanina’s statement by citing the following months and their scriptural sources (all post-exile), Nissan in Esther (3:7), Kislev in Nechemia (1:2), and Tevet in Esther (2:5).

Though not included in the Gemara in Rosh Hashanah, through a scriptural search, we find mention of the month of Shevat in Zecharia (1:7), Adar and Nissan in Esther (3:7), Sivan in Esther (8:9), and Elul in Nechemia (6:15), which are all post-exile references found only in the prophets and Hagiographa.

However, we find no scriptural mention of Iyar, Tammuz, Av and Marcheshvan. Our tradition, based on the Gemara’s statement (“The names of the months were brought up with them…”), is that these names, too, were brought up from Babylonia. Indeed, when the exiles came to Babylonia they found a society that used a lunar calendar similar to ours and that they were quite knowledgeable of astronomy.

Eventually, the Babylonian names for the months were popularly adopted. The only names for months that were used were the 12 that we currently use – in the following order: Nissan, Iyar, Sivan, Tammuz, Av, Elul, Tishrei, Marcheshvan, Kislev, Tevet, Shevat, and Adar. This is possibly due to their (the Babylonians, unlike us) having no real need of a leap year. We, on the other hand, need the occasional leap year in order to maintain the seasonal integrity of our festivals.

There was no extra Babylonian name to be used for the purpose of a “leap” month that needed to be added to the Jewish year, and certainly our sages did not create another Babylonian name for that purpose.

As to which of the two Adars is considered the “leap” – or extra – month, it is actually the second, which we refer to as Adar Sheni (or Adar Bet), meaning the second Adar. This is because the Talmud (beraita, Rosh Hashanah 7a) refers to Nissan (the first of the months and that which immediately follows Adar) as the Rosh Hashanah of ibburin – intercalations.

The Gemara concludes that normally (when ibbur was done only through testimony presented to beit din, before our fixed calendar was established), the leap month can only be added before Purim.

The Gemara cites this halacha (Pesachim 6a) to prove the point, “We inquire [study in depth] the laws of Pesach before Pesach for 30 days,” and explains that once they have already begun that study, they will come to violating the laws of chametz (on Pesach).

Rashi (s.v. ‘ati l’zilzulei b’chametz’) explains that this refers to the practice of the rabbis to publicly lecture on the subject of the laws of Pesach for one entire month preceding the festival. Once this process has commenced, people will not accept the testimony of the messengers of beit din that an extra month has been added. In such case, the result will be that they will end up eating chametz on what is actually the “real” Pesach.

(To be continued)

 Rabbi Yaakov Klass can be contacted at


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Rabbi Yaakov Klass, rav of Congregation K’hal Bnei Matisyahu in Flatbush, Brooklyn, is Torah Editor of The Jewish Press. He can be contacted at