"The first day of the week is mentioned in the New Testament only eight times, and is not in a single instance spoken of as a Sabbath, a day of rest, or a sacred day. It is simply called the first day of the week.
On the other hand, inspiration gives the seventh day of the week in the New Testament the sacred title of the Sabbath fifty-nine times.
John 20
1 The first day of the week came Mary Magdalene early,
when it was yet dark, unto the sepulcher, and saw the stone
taken away from the sepulcher."
James White