'First Day' in the Bible

Now on the first day of the feast of Unleavened Bread, when the Passover lamb is sacrificed, Jesus' disciples said to him, "Where do you want us to prepare for you to eat the Passover?"

And very early on the first day of the week, at sunrise, they went to the tomb.

[[Early on the first day of the week, after he arose, he appeared first to Mary Magdalene, from whom he had driven out seven demons.