The Reason For The Feast Of Unleavened Bread 

Although we can in general speak of the Passover/Feast of Unleavened Bread season, they are given distinction in the law of Moses and have subtle differences in the plan of coming out of Egypt. The Passover a meal on the night of the final judgement and the Feast for the day that Israel left Egypt as a nation from Ramesses to Succoth. Passover more pensive and solemn and the Feast being more festive and joyful.