On the first day of the second month in the second year after the people of Israel left Egypt, the Lord spoke to Moses there in the Tent of his presence in the Sinai Desert. He said,
you are permitted to observe it one month later instead, on the evening of the fourteenth day of the second month. Celebrate it with unleavened bread and bitter herbs.
and on the evening of the fourteenth day of the first month they did so in the Sinai Desert. The people did everything just as the Lord had commanded Moses.