The holiday of Pesach, or Passover, is an annual week long festival commemorating the Exodus of the Jews from Egypt and slavery. The festival begins on the 15th day of the Hebrew calendar month of Nisan—which derives its name from the passing over of the homes of the Israelite slaves during the tenth plague. Passover begins in the evening at sundown prior to the first full day of the festival. In 2017, Monday, April 10 is the first evening (at sundown) of Passover; Tuesday, April 18 is the first full day. In many Reform Jewish communities, Passover is celebrated for seven days, not eight. In more traditional Jewish communities—including both Orthodox and Conservative communities—Passover is celebrated for eight days.