'First Day' in the Bible

And on the first day of unleavened bread, when the Passover lamb is put to death, his disciples said to him, Where are we to go and make ready for you to take the Passover meal?

And very early after dawn on the first day of the week, they came at the time of the coming up of the sun to the place where the body had been put.

Now when he came back from the dead early on the first day of the week, he went first to Mary Magdalene, from whom he had sent out seven evil spirits.