Why does the Jewish leap year always consist of two Adars? Why specifically Adar?
Summary of our response up to this point: We cited several sources for the law that we only intercalate Adar, including the 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.
* * * * *
Tosafot’s explanation for why we only intercalate Adar is quite difficult to understand. In truth, the only logical month to intercalate is Adar, but not for Tosafot’s reason. If we would intercalate Nissan or Iyar, we would be presented with a problem when counting the omer. There are 49 days from the second day of Passover, the 16th day of Nissan – when we start to count the omer – to Shavuot, the 6th day of Sivan. If we added a month anywhere between the two, Shavuot wouldn’t fall out in Sivan.
But this just raises another question: Does Shavuot actually need to be in Sivan? According to the Gemara, Shavuot need not fall out on a specific date. We find the following in Rosh Hashanah 6b: R’ Shmaya taught that Shavuot at times falls on the 5th of the month, at times on the 6th, and at times on the 7th. How so? If both Nissan and Iyar are full, 30-day months, then it falls on the 5th. If both are deficient, 29-day months, then it falls on the 7th. If one is full and the other deficient, then it falls on the 6th. (Of course, with our set calendar, Nissan is always full and Iyar is always deficient. This means that Shavuot always falls on the 6th – and in the diaspora, the second day always falls on the 7th.)
Further proof that the specific day of Shavuot is not fixed is found in the Kiddush and Shemoneh Esreh for the three festivals where Shavuot is referred to as “zman matan Torateinu – the time of our being given the Torah.” It makes sense that “zman – time” is used in reference to Pesach and Sukkot (“zman cheiruteinu – the time of our freedom” and “zman simchateinu – the time of our joy”) since these holidays are weeklong festivals. But Shavuot is just a one-day festival (two days in the diaspora). It rightly, therefore, should be referred to as “yom matan Torateinu – the day of our being given the Torah.” Since the term zman is used, it is clear that our sages, who fixed the texts of our prayers, were aware that Shavuot need not fall out on any specific day of Sivan.
However, the month is fixed as the Torah specifically states (Exodus 19:1), “Bachodesh ha’shelishi l’tzeit bnei Yisrael me’eretz Mitzrayim ba’u midbar Sinai – 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 is in the third month, and, as such, Shavuot must fall in the third month.
(To be continued)