|New Moon over sun-lit face of Earth|
Genesis 1:14-15; 16-17; 18-19; On the fourth day Yehawah Eloheyem set in order the sun, moon, and stars. The great light of the sun would established the 24 hour period that governs the day. The lesser light of the moon would be used to calculate monthly events called (Moedim = appointed times or seasons) and the passing of years. The Moedim are the High Holy appointed times of Passover, Unleavened Bread, Pentecost, Trumpets, Atonement, and Tabernacles.
Genesis 2:2-3; On the seventh day Yehawah Eloheyem rested and established His seventh day Sabbath as Holy. The sun is used to calculate the 24-hour day and count to the weekly seventh day Sabbath.
The moon is only used to establish the appointed times for the seasonal Moedim. The 29 1/2 day moon cycle forms a predictable pattern that coincides with the solar equinox. Both the earth and moon follow elliptical orbits that produce observable variations that repeat every 19 solar years. The term month originated from the observation of lunar cycles. The 29 1/2 lunar cycle comes to an end as a new moon occurrs during the daylight hours of day 30. The new moon passes between the sun and the day-lit face of the earth. Every other month there will be an additional day added and the new moon celebration will be completed on day 31.
see also: NEW MOON n COUNTING
It should seem obvious from simple mathematics that the seventh day Sabbath calculation will not consistently synchronize with a 29 1/2 day lunar cycle. There is a strange error made by some Bible students that assume the lunar cycle must be used to establish the seventh day Sabbath.