Leshon Ima with Dr. Rachel Zohar Dulin, Special To The Dayton Jewish Observer

So far this year, we’ve celebrated the holidays earlier than usual. That Chanukah, for example, coincided with Thanksgiving, made it clear that this is an “intercalation” year in which an adjustment had to be made to assure that the Jewish holidays will be celebrated in their seasonal time.

Rosh Hashanah should fall in the autumn, Chanukah should be celebrated during the dark days of winter. Pesach should mark nature’s renewal in the spring and Shavuot should be at the beginning of summer.

The adjustment of the Jewish calendar was designed by Rabbi Hillel II (359 C.E.) and is called ibur hashanah. Shanah in Hebrew means year and ibur means intercalation, conception, and growth. The word is derived from the verb iber meaning to impregnate (Job 21:10).

Shanah meuberet is an intercalation year, a leap year, the year in which an extra month is added in order to adjust between the lunar cycle of 354 days and the solar cycle of about 365 days.

The month added to the calendar is Adar, the very same month in which we celebrate Purim. The reason Adar was chosen is because it was the last month of the Hebrew calendar in biblical times, marking the end of winter and ushering in the month of Nisan, the first month of the new year.

In the time of the Mishnah, the rabbis changed the Hebrew calendar and declared the year begins in the fall and not in the spring, but ibur hashanah stayed in its place (Rosh Hashanah 1:1).

There are a few expressions in Hebrew in which ibur is used. For example, ibur hachodesh, intercalary month, is the month in which a day is added (P’sachim 4:9) and sod haibur literally the secret of intercalation, points to the knowledge of the adjustment system itself (Rosh Hashana 20).

We should also mention the phrases iburah shel ir, a city sprawl, the suburbs (Nedarim 7:8) and ibur din, transgression of the law (Sh’mot Raba 30).

The consequence of having two months of Adar in a shanah meuberet is that the celebration of Purim is doubled. That is to say, during a leap year, Purim is celebrated once as Purim Katan, namely small Purim, on the 14th day of the first Adar and then it is celebrated in a big way on the 14th day of the second Adar (Megillah 6b).

There are no specific instructions for the observance of Purim Katan but one does not mourn or fast on this date. A festive meal is eaten but the Megillah is not read.

Dr. Rachel Zohar Dulin is a professor of biblical literature at Spertus College in Chicago and an adjunct professor of Bible and Hebrew at New College of Florida.

To read the complete March 2014 Dayton Jewish Observer, click here.