Page 12 "Talking It Over" by Glenn Ford
First night of the feast of the Passover meal (evening Nisan 14); (Exodus 12:8-11) and (Luke 22:15-20) eat roasted lamb (save none), eat bitter herbs, unleaven bread and drink fruit of the vine. Note: Biblical days are from evening to evening.
First morning of the unleaven bread week (Nisan 14) have a Holy Convocation (study Bible and DO NOT go to work: Holy Holiday) (Exodus 12:16). Seven days we shall eat unleaven bread (Exodus 12:15). NO LEAVEN in house! (Yeast, Sodium Bicarbonate, Baking Powder and Baking Soda).
Seventh day (Nisan 21) (Exodus 12:16) and (Exodus 13:6), Holy Convocation and a Feast unto the Lord (another Holy Holiday, NO Work).
Passover = 7 nights and 7 days. Nisan 14 at evening - Nisan 21 at evening (always: FOREVER) = (Exodus 12:17) and (Luke 22: 15-20).
P.S. Only other alternative dates (the following month): Iyar 14 at evening - Iyar 21 at evening (Nu. 9:6-13). Evening to evening.