Christmas Day, marking the birth of Jesus Christ, will also mark the first night of Hanukkah, the Jewish holiday that commemorates the rededication of the Temple in Jerusalem nearly two centuries before, in a rare joint occurrence.

Christmas is observed on the 25th of December, and Hanukkah (also spelled Chanukah) falls on the 25th day of the Jewish month of Kislev. But the Christian world uses a solar calendar, while the Jewish calendar is both solar and lunar.

The lunar year is eleven days shorter than the solar year, meaning that Jews add an extra month once every several years — a leap year — to keep the holidays in the same season. (The Islamic world, whose calendar is lunar, observes its holidays