Halocho #681 - It's going to be a long year

Some years the Jewish calendar have 12 months, the rest (7 out of 19) are leap-years with 13 months.

This year - 5771 - has 13 months; the 11th month - Shevat - is followed by Adar-I and then Adar-II. Purim is in Adar-II

Jewish months alternate between being 29 and 30 days long.

However, the months of Marcheshvan and Kislev sometimes both have 30 days (a full year), sometimes both have 29 days (a missing year) and sometimes follow the regular order with Marcheshvan having 29 days and Kislev 30.

As a result, Chanukah (which starts on 25 Kislev and lasts 8 days) sometimes ends on 2 Tevet and sometimes on 3 Tevet.

This year - 5771 - is a "full year" with both Marcheshvan and Kislev having 30 days.

Adar-I is always 30 days long, even though Shevat is 30 days long.

This year - 5751 - is 385 days long, a full 55 weeks. As a result, Pessach will once again start on Tuesday, and Rosh Hashana will once again be on Thursday-Friday.

Source: Kitzur Shulchan Aruch 221:4

- Danny
Tuesday, 25 Marcheshvan 5771