Hanukkah, also known as the Festival of Lights, is a Jewish festival commemorating the recovery of Jerusalem and the subsequent rededication of the Second Temple at the beginning of the Maccabean revolt against the Seleucid Empire in the 2nd century BCE. Hanukkah is observed for eight nights and days, starting on the 25th day of Kislev according to the Hebrew calendar, which may occur at any time from late November to late December in the Gregorian calendar. The festival is observed by lighting the candles of a candelabrum with nine branches, commonly called a menorah or hanukkiah.

Source: Wikipedia