1) Obviously he was referring to Jewish customs. You think the Greeks knew nothing about the Jews? 2) At dawn on the day after the Sabbath, Mary Magdalem and the other Mary came near to contemplate the tomb. So?
The point is ......they did not come at dawn. The came "Late on Sabbath" and found the tomb empty!.....on the Sabbath! While they were there (sunset Sabbath) the new day began and it was called the first day of the week. In that time zone, at that time of year it would have been about 5:00 to 6:00 p.m. on Saturday.....our time.
Matthew 28:1 Verse 6 says "HE is risen"....past tense!