The Jewish calendar is a lunisolar calendar, or "fixed lunar year," based on twelve lunar months of twenty-nine or thirty days, and a weekly cycle of seven days, mirroring the seven-day period of the Book of Genesis in which the world is created.

How Christ celebrated the calendar while on earth

Hebrew Calendar ● Wiki

From the new moon, the Babylonians celebrated every seventh day as a "holy-day", with prohibited activities, to conduct offerings to a different god and goddess. The last week would be longer (ie. 9 days), to accommodate for the new moon, which would start a new week and month.

Original source of "New Light"

Babylonian Calendar ● Wiki

Jonathan David Brown, a former convict, was the first sabbath keeper in the 20th century to begin the practice of counting the Sabbath from the New Moon day rather than using the modern seven day week.

20th Century source of "New Light"

Jonathan David Brown ● Wiki

There are 613 commandments of God in 4 different books in the Bible, Exodus, Leviticus, Numbers and Deuteronomy.

However, there is no mention of a new moon in either of these books. In fact, the first mention of a new moon comes in I Samuel.

613 Mitzvot ● Wiki

1 lunar cycle = 29.530589 days.

Not Divisible by Seven.

Lunar Phase ● Wiki

Fourth Commandment: "Six days shalt thou labour, and do all thy work: But the seventh day is the sabbath of the LORD thy God." Exodus 20:9, 10.

Seven days - No mention of any exception.

Ten Commandments ● Wiki