Passover (Pesach) is the holiday we celebrate in the spring. It begins on the 15th day of Nisan (on the Hebrew calendar) – this year, it arrives at nightfall on April 2. Passover commemorates the exodus and freedom of the Israelites from ancient Egypt. As described in the Book of Exodus, Passover marks the "birth" of the Children of Israel who become the Jewish nation, as the Jews' ancestors were freed from being slaves of Pharaoh and allowed to become followers of God instead. Together with Sukkot and Shavuot, Passover is one of the three pilgrim festivals (Shloshet Ha'Regalim) during which the entire Jewish population made a pilgrimage to Jerusalem, at the time when the Temple in Jerusalem was standing. Outside of Israel, Passover is traditionally celebrated for 8 days, with the first two days and last two days celebrated as full festivals. The intervening days are known as Chol HaMoed ("festival weekdays"). The primary symbol of Passover is the matzah, a flat, unleavened "bread" which recalls the hurriedly-baked bread that the Israelites ate after their hasty departure from Egypt.