'First Day' in the Bible

Now on the first day of the week cometh Mary Magdalene early, while it was yet dark, unto the tomb, and seeth the stone taken away from the tomb.

When therefore it was evening, on that day, the first day of the week, and when the doors were shut where the disciples were, for fear of the Jews, Jesus came and stood in the midst, and saith unto them, Peace be unto you.