Thank you for contacting BibleAsk.
Lunar Sabbath believers redefined a day as being just the day time, instead of the Bible‘s description of a day which is “evening and morning” (Genesis 1:5,8,13, 18, 23, & 31). To say that a day is made up of an evening and morning will cause conflict to the interpretation that the Sabbath always falls on the 15th, as the children of Israel would have had to travel on the 15th when they escaped Egypt:
“And they took their journey from Elim, and all the congregation of the children of Israel came unto the wilderness of Sin, which is between Elim and Sinai, on the fifteenth day of the second month after their departing out of the land of Egypt.” Exodus 16:1
Since we know that the children of Israel would not have packed, traveled, and set up camp on the Sabbath, Lunar Sabbath believers teach that the Sabbath is only the period of day light while the dark part of the day is not Sabbath nor holy. This way, in relation to the start of the Exodus, it is explained that after the 10th plague, when first born died in Egypt, that when the sun rose, the Children of Egypt stayed in their houses the whole day, to observe the Sabbath, then upon sunset they went to the Egyptians asking for money, then began their Exodus.
The Lord says, “And in vain they worship Me, teaching as doctrines the commandments of men” (Matthew 15:9).
In His service,
“Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men,
after the rudiments of the world, and not after Christ.” Colossians 2:8