Background: Why Is There a 13th Month?

The Torah commands us to keep a lunar calendar.1 A lunar cycle is approximately 29.5 days, and a year of 12 lunar months contains 354 days.2 However, a solar year is 365 days long, making a lunar year approximately 11 days shorter than a solar year.

We are also commanded to keep the holidays in their proper seasons (e.g., Passover in spring and Sukkot in autumn).3 In order to get keep the lunar year in sync with the seasons, which are based on the solar year, we add a full month every two or three years (seven times in a 19-year cycle). Such a year is a Jewish leap year, which is called a shanah m'uberet, a “pregnant year,” or perhaps more properly an “enlarged year,” since it is temporarily larger than usual.

The Jewish months start with the month of Nissan and ends with the month of Adar. We add the extra month at the end; thus, a Jewish leap year has two months of Adar (Adar I and Adar II). This, of course, brings us to the question: In which month do we celebrate Purim, which is observed on Adar 14?

When Is Purim?

There is an opinion in the Talmud that Purim should be celebrated in Adar I based on the rule ain maavirin al hamitzvot, “one does not ‘pass over’ or forego the performance of the mitzvahs”; rather, when presented with the opportunity to perform a mitzvah, one should do so immediately. Thus, it is reasoned that Purim should be celebrated at the first opportunity, i.e., Adar I. Nevertheless, the halachah follows the opinion that Purim is celebrated in Adar II, for it is closest to the month of Nissan, and we want to “connect redemption to redemption,” i.e., the redemption of Purim to the redemption of the Exodus, which is in the month of Nissan.4

While We Are on the Subject of Purim ...

Although Purim is celebrated in Adar II, the days 14 and 15 Adar I are known as Purim Katan (“Small Purim”) and Shushan Purim Katan (“Small Shushan Purim”) respectively. On these days, Tachanun (penitential prayers) are omitted,5 one doesn’t fast, and eulogies are generally not made.6

It is interesting to note that in the Second Temple era, when there was not yet a fixed calendar, if the extra month of Adar II was only added after Purim was celebrated, the Jews would celebrate Purim a second time in Adar II.

Read more about how the leap year operated in ancient times

Did the Miracle of Purim Happen in Adar I ?

Although we celebrate Purim in Adar II, there is a fascinating and intriguing statement in the Jerusalem Talmud regarding the timing of the Purim story:

[Said] Rabbi Levi in the name of Rabbi Choma, the son of Rabbi Chaninah: “That year [of the miracle of Purim] was a leap year. Why do we say this? For it is written [regarding Haman’s lottery to determine the best month to annihilate the Jews], ‘. . . Cast the pur, that is the lot, before Haman, from day to day and from month to month, to the 12th month, it is the month of Adar.’78

How does this verse indicate that that year was a leap year?

Some read the verse as saying: “the lot fell out on [what would have been] the 12th month [but was actually the 13th month because there was an additional] Adar.”9 According to this opinion, the miracle happened on 14 Adar II, the day we celebrate as Purim during a leap year.

Others, however, explain that the Talmud is actually stating that Haman’s lottery fell out on the 12th month, Adar I in a leap year.10 But then why do we celebrate Purim in the second Adar?

One explanation is that according to the calculations, that year was due to be declared a leap year.And as such, when Haman’s lottery fell out on the 12th month, it would have been Adar I. (According to some, this actually excited Haman, for he figured that Adar I is bereft of any merits11). However, ultimately, the rabbis didn’t make it a leap year, and there was only one Adar.12

Regardless, according to the Babylonian Talmud, the year of the miracle wasn’t (nor was it ever expected to be) a leap year.13

Celebrating Life

In the concluding gloss of the first book of the Code of Jewish Law, Rabbi Moses Isserlis writes: “There are those who say that one is obligated to increase in joy and feasting on the 14th of Adar I (i.e., Purim Katan); however, this is not the practice. Nonetheless, one should increase somewhat his joy and feasting in order to fulfill the words of those who are stringent , [as it states in Proverbs,] ‘One who is of good heart is festive always.’1415

The Lubavitcher Rebbe points out that at first glance it seems strange that this was the day chosen to teach us the principle that one should always rejoice. After all, other than the custom to add something extra to your meal, there isn’t much we do on this day. Yet, that is the point. Joy is not restricted to days on which there are great happenings, such as the conclusion of the Torah on Simchat Torah or the grand Purim feasts a month from now. Even on seemingly mundane days, we have to be in a constant state of joy. For joy breaks all boundaries, including those of our exile, and hastens the ultimate redemption.16

May it be speedily in our days!