LEAP YEAR, refers to the 13-month year in the Jewish *calendar. Leap year results from the intercalation (Heb. עִבּוּר, "pregnancy") of an additional month, called Adar Sheni ("Second Adar") or Ve-Adar ("and Adar"). Adar, the regular 12th month, is then called Adar Rishon ("the first Adar"). Leap year is a means through which the annual difference of 11 days between the solar year and the lunar year is adjusted. A leap year occurs seven times in every cycle of 19 years (maḥazor ḥammah), namely in the years: 3, 6, 8, 11, 14, 17 and 19 of the cycle. The first Adar has 30 days, the second Adar 29. The number of days in a leap year is either 383, 384, or 385. The period between the first of Nisan and the first of Tishri is always 177 days. The intercalation of years was already practiced by the Sanhedrin in the Hasmonean and mishnaic periods. Among the factors then taken into consideration were the ripened state of the Omer ("barley") offered on Passover, and that of the bikkurim ("first fruits") sacrificed on Shavuot. It also depended on whether the roads and bridges were passable so that the pilgrims could go to Jerusalem for the Passover festival, and whether the ovens for the paschal-lamb sacrifices were already dry after the rainy season. (See: Tosef., Sanh. 2:12; Sanh. 11aff.)
Ḥ.S. Slonimski, Yesodei ha-Ibbur, ve-Hu Seder Ḥeshbon Ibbur ha-Shanim… (1865); Maimonides, Ma'amarha-Ibbur (1911), ed. by E. Donner; J. Barb, Kunteres Sod ha-Ibbur… (1897); see also bibl. of *Calendar article.
Source: Encyclopaedia Judaica. © 2008 The Gale Group. All Rights Reserved.