When It Occurs

Purim is celebrated on the 14th day of Adar, which is generally in March. The 13th of Adar is the day that Haman chose for the extermination of the Jews, and the day that the Jews battled their enemies for their lives. On the day afterwards, the 14th, they celebrated their survival. In cities that were walled in the time of Joshua, Purim is celebrated on the 15th of the month, because the book of Esther says that in Shushan (a walled city), deliverance from the massacre was not complete until the next day. The 15th of Adar is referred to as Shushan Purim.

In leap years, when there are two months of Adar, Purim is celebrated in the second month of Adar, so it is always falls one month before Passover. The 14th day of the first Adar in a leap year is celebrated as a minor holiday called Purim Katan, which means "little Purim." There are no specific observances for Purim Katan; however, a person should celebrate the holiday and should not mourn or fast. Some communities also observe a "Purim Katan" on the anniversary of any day when their community was saved from a catastrophe, destruction, evil or oppression.

The Purim holiday is preceded by a minor fast, the Fast of Esther, which commemorates Esther's three days of fasting in preparation for her meeting with the king.