In the passage you quoted, I'm not sure why you think it refers to the beginning of the night. I don't know a lot about religion though I'm aware that in some religions the Sabbath is on Saturday and ends at sunset (or perhaps, as you said, 6pm). Also, that the first day of the week can be seen as Sunday, though a lot of people would say that Monday is the first day of the week.
To me, "In the end of the sabbath, as it began to dawn" would be somewhat confusing. "At the end of the sabbath (or any other day) would suggest towards midnight. But "as it began to dawn" would mean sunrise. So I would say there's a gap where there are a few hours missing!
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