'First Day' in the Bible

On the first day of the festival of Unleavened Bread, on which it was customary to kill the Passover lamb, Jesus' disciples said to him, "Where do you wish us to go and make the preparations for you to eat the Passover supper?"

Then very early on the first day of the week they went to the tomb, when the sun had just risen.

Now after he had risen, early on the first day of the week, he appeared first to Mary of Magdala, from whom he had driven out seven evil spirits.