 FACT: In the movie, the 10th Plague (killing of the firstborn of the  Egyptians) occurs with a crescent moon showing. However, the Jewish  holiday of Passover, which coincides with the 10th Plague, occurs on  the 14th day of the month of Nissan, according to the biblical book  of Exodus. Because the Jewish calendar is based on a lunar cycle,  there would be a full moon on the 14th of the month.