Really?  And wouldn't this be the OBVIOUS question that any of us would ask when contemplating this message?  
The person making this claim is once again guilty of answering the matter before they hear it (
Proverbs 18:13).  By
this way, they bring shame and folly to themselves.

This is easy.

Everyone is familiar with
Exodus 20:8-12.  The nay-sayers use it as a club while ignoring Deuteronomy 5:12-15,
the second time the 4th commandment is repeated in the Torah...

Keep the sabbath day to sanctify it, as YHVH thy Elohim hath commanded thee.
Six days thou shalt labor, and do all thy work:
But the seventh day is the sabbath of YHVH thy Elohim: in it thou shalt not do any work, thou, nor thy son, nor thy
daughter, nor thy manservant, nor thy maidservant, nor thine ox, nor thine ass, nor any of thy cattle, nor thy
stranger that is within thy gates; that thy manservant and thy maidservant may rest as well as thou.
And remember that thou wast a servant in the land of Egypt, and that YHVH thy Elohim brought thee out thence
through a mighty hand and by a stretched out arm: therefore YHVH thy God commanded thee to keep the sabbath
Deuteronomy 5:12-15

Here the fourth commandment is linked to Israel's deliverance from Egypt.  And what day were they delivered?  The
15th day of the first month.  All the weekly Sabbaths in Scripture that can be date identified always fall on the 8th,
15th, 22nd or 29th days of the lunar month.  This is another witness of this fact.
9.  Lunar Sabbath keeping is utterly incompatible with the Fourth Commandment, which
says nothing about establishing the weekly, Seventh-day Sabbath on a lunar cycle, but
rather establishes the Seventh-day Sabbath on the seven day cycle of Creation Week.
Objections to the Calendar of Creation: