Murray, your idea of nominationg which is the first day of the week in order to find which is the seventh will give us 7 possibilities.
Going back to an earlier source:
"Now upon the first day of the week, very early in the morning, they came unto the sepulchre, bringing the spices which they had prepared, and certain others with them." (Luke 24:1, King James Version)
Christ rose again on a Sunday, and this is the reason Christians celebrate Sunday. The desciples had not gone to the sepulchre on the previous day to tend the body, because they were still tied to Jewish religious observances which prevented any 'work' on the Sabbath (Saturday).
Our observance of Sunday, and willingness(?) to work on a Saturday follow on from Jesus healing the sick on the Sabbath, and having to justify himself to the Pharisees.

Nigel