The Catechism says:
2174 Jesus rose from the dead "on the first day of the week." Because it is the "first day," the day of Christ's Resurrection recalls the first creation. Because it is the "eighth day" following the sabbath, it symbolizes the new creation ushered in by Christ's Resurrection. For Christians it has become the first of all days, the first of all feasts, the Lord's Day (he kuriake hemera, dies dominica)—Sunday:
but He was not ressurected on the 1st day...He was resurrected on the third day.
We all gather on the day of the sun, for it is the first day [after the Jewish sabbath, but also the first day] when God, separating matter from darkness, made the world; and on this same day Jesus Christ our Savior rose from the dead.
nice thought, but is it correct? Can you prove it. Simple math would say no.
Sunday—fulfillment of the sabbath
2175 Sunday is expressly distinguished from the sabbath which it follows chronologically every week; for Christians its ceremonial observance replaces that of the sabbath. In Christ's Passover, Sunday fulfills the spiritual truth of the Jewish sabbath and announces man's eternal rest in God. For worship under the Law prepared for the mystery of Christ, and what was done there prefigured some aspects of Christ: