Mark 14:12

12On the first day [of the festival] of 14:12 This remembrance lasted eight days. The Passover lambs were selected on the 10th of Nisan (March/April) and sacrificed on the 14th of Nisan (the first day of the feast). The Passover meal was eaten that same night (the 15th of Nisan). Passover was immediately followed by the Feast of Unleavened Bread (15-21 Nisan). The terms “Passover” and “The Feast of Unleavened Bread” were used interchangeably.Unleavened Bread, when [as was customary] they sacrificed the Passover lamb, His disciples asked Him, “Where do You want us to go and prepare for You to eat the Passover?” [Matt 26:17-19; Luke 22:7-13]