Genesis 1:3 And God said, Let there be light: and there was light.
4 And God saw the light, that it was good: and God divided the light from the darkness.
5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
A "day" (meaning when there is light) is counted as a day by either method. The early and modern Hebrews/Jews begin counting a "new day" after dark, the west begins the "new day" in the middle of the night (the night being split into two halves) - not too kosher IMHO, as it goes against the Almighty's way of keeping time.
The Hebrew month begins with the sighting of the new moon (after dark) - the evening AND morning of that day, prior to the sighting, IS the last day of the month.
High Sabbaths can indeed fall on weekly Sabbaths or any other day of the week for that matter.
That's the way it has been kept for thousand of years, even during Yeshua's first time on earth. There is no controversy that I'm aware of in the scriptures concerning this.
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>> “the evening AND morning of that day, prior to the sighting, IS the last day of the month.” <<
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Not sure what you’re saying there, but....
The evening (at the sighting) and the morning following are the first day of the month.
Evening begins every Biblical day.
This is why the New Testament says that they “came together on the first day of the week” when they met in the evening for Havdalah at the close of the Sabbath.
By the Roman calendar, it was Saturday evening, but by the Biblical calendar it was the first day of the week.
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