The 7th and last day of the Feast of Unleavened Bread (Pesah) is the 21st day of the 1st month of Abib/Nissan. This is considered a convocation day and a Sabbath day therefore no servile work is done on this day. This the traditional celebration of the crossing of the Red Sea (Biblical Feasts, 2016).
Reference: The Biblical Feast Days. Retrieved on Feb. 29, 2016. http://biblelight.net/feasts.html