On what day of Nisan does Passover begin?

Passover begins on the 15th day of Nisan.

In the Hebrew calendar, Passover starts at sunset as the 14th of Nisan ends and the 15th begins. This reflects the Hebrew system of reckoning days from evening to evening, so the first Seder is held on the evening that begins 15 Nisan. In Israel, Passover lasts seven days; in many traditional Jewish communities outside Israel, it is observed for eight days.

The date is tied to the biblical Exodus narrative. The Israelites were instructed to eat the Passover offering with unleavened bread and bitter herbs, recalling their hurried departure from Egypt. The festival later became a central annual commemoration of liberation and covenantal identity.

The 14th can cause confusion because preparations and the slaughter of the ancient Passover sacrifice were associated with that date, while the festival itself begins on the 15th. The Gregorian date changes each year because Nisan is part of a lunisolar calendar.