Passover is observed on the 14th day of the Jewish religious calendar in the month called Nisan ( Nissan). The start of the month begins with the sighting of the first crescent moon after New Moon. This means that Passover occurs just after the Full Moon since the Synodic month is 29.5 days long so that Full Moon happens on Day 14.75, but the first sighting of the crescent moon usually happens when it is about 20 - 24 hours old. This means that Passover happens about 14+1 -14.75 = 1/4 day after the Full Moon by my estimates.