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Why does the Jewish leap year always consist of two Adars? Why specifically Adar?

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Summary of our response up to this point: We cited several sources for the law that we only intercalate Adar – including Bavli (Rosh Hashanah 7a and Sanhedrin 12a), Yerushalmi (Sanhedrin 1:2), and Rambam (Hilchot Kiddush Hachodesh 4:1). However, your question is a good one: Why?

Tosafot (Sanhedrin 12a) offers a scriptural reason: to ensure that Adar will remain the twelfth month, as it is referred to in Megillat Esther (3:7).

We noted the reason for any intercalation – the 11-day discrepancy between the lunar and solar years. The lunar year is 354 days, which is the approximate time it takes for 12 new moons to occur. The solar year is 365 days, which is the approximate time it takes for the earth to complete one solar revolution. Thus every several years, an extra month is added to the Jewish lunar year, allowing the lunar and solar years to be in sync again and ensuring that the holidays are celebrated in their correct seasons.

The only logical month to intercalate is Adar. If Nissan or Iyar were intercalated, we would be presented with a problem when counting the omer. We count 49 days starting on the second day of Pesach, Nissan 16, until the omer’s conclusion at Shavuot, the 6th day of Sivan. If we would add a month anywhere between the two, Shavuot would no longer occur in Sivan.

While Shavuot is not necessarily required to fall on a fixed day, Exodus 19:1 specifically states that “in the third month [Sivan] from the exodus of the Children of Israel from the land of Egypt, they arrived in the wilderness of Sinai.” Thus, the Torah is emphatic that the giving of the Torah took place in the third month. As such, Shavuot – when we celebrate being given the Torah – must fall in Sivan.

Last week, we examined scriptural mentions of specific dates for other holidays. Parshat Pinchas tells us that Rosh Hashanah is on the first day of the seventh month, Yom Kippur on the tenth day of the seventh month, and Sukkot on the fifteenth day of the seventh month. If we were to intercalate any of the months preceding these festivals, they would not occur in the seventh month as the Torah mandates.

The Gemara (Rosh Hashanah 7a) intimates that we only intercalate right before Nissan because the Torah (Deuteronomy 16:1) requires Passover to fall in the spring. The Rambam writes explicitly that we make two Adars to prevent Passover from sometimes falling in the winter. Pirush Rabbeinu Ovadia adds that in Adar, beit din examines the crops to see whether the wheat has already ripened, a sign that spring has arrived. If it has, there is no need to intercalate that year.

Clearly there are biblical sources to rely on. Why, then, does Tosafot cite a verse in Esther for intercalating Adar? Furthermore, it seems that the verse in Esther refers to a regular year, not a leap year. Otherwise, it would not have referred to Adar as the twelfth month.

* * * * *

My understanding is that the year of the Purim story was a regular one of twelve months. I make this assumption because I find no indication otherwise anywhere in Megillat Esther or the Talmud.

Rabbi Yosef Grossman in Otzar Erchei HaYahadut (p. 28 – “Adar Sheni”) writes: “The reason for the importance of Adar Sheni [i.e., why we celebrate Purim and read the parshiyot this month and not in Adar Rishon] is because in the year of the issuance of Haman’s evil edict against the Jews, these events occurred during Adar Sheni. This means that it was a leap year consisting of thirteen months.”

Yet, after a thorough search, I could not find the source upon which Rabbi Grossman bases his conclusion. And as previously mentioned, I find Tosafot (Sanhedrin 12a) problematic – specifically their statement that we only intercalate Adar because of a verse in Esther (3:7) that calls Adar the twelfth month. It may have been the twelfth month that year, but the verse doesn’t necessarily imply that it must be so every year.

Now, according to Rabbi Grossman, and based on the Gemara’s conclusion that Purim and the associated mitzvot are celebrated and observed during the Adar closest to Nissan (i.e., Adar Sheni), Adar winds up being the thirteenth month. Even so, Tosafot concludes that Adar is the twelfth month and uses this as proof that we only intercalate Adar so that it remains the twelfth month. This reasoning differs from that of the Gemara (Rosh Hashanah 7a), which states that we intercalate only right before Nissan because the Torah (Deuteronomy 16:1) instructs: “Shamor et chodesh ha’aviv v’asita pesach la’Shem Elokecha – You shall observe the month of springtime and perform the paschal offering.” This verse clearly indicates that Passover must fall in the spring (aviv).

(To be continued)


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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


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