Ezekiel 46:1  Thus saith Yahowah; The gate of the inner court that looketh toward the east shall be shut the six working days; but on the sabbath it shall be opened, and in the day of the new moon it shall be opened.

3 And shall worship the people of the land the door of gate that, on the Sabbaths and on the new moons before Yahoweh.

Isaiah 66:23  And it shall come to pass, [that] from one new moon to another, and from one sabbath to another, shall all flesh come to worship before me, saith Yahowah.

Sabbath The Jewish Encyclopedia 590
Probable Lunar Origin.
-Critical View: The Sabbath depending, in Israel's nomadic period, upon the observation of the phases of the moon, it could not, according to this view, be a fixed day. When the Israelites settled in the land and became farmers, their new life would have made it desirable that the Sabbath should come at regular intervals
Assyrian Analogues. Dissociated from the moon the Sabbath developed into a day of rest for the workers and animals on the farm … … The Assyrian calendar seems to disclose an effort to get rid of the movable Sabbath in favor of the fixed.

From The Universal Jewish Encyclopedia
[410] Holiday Prayers
Holidays
... 1. Sabbath and New Moon (Rosh Hodesh), both periodically recurring in the course of a year. The New Moon is still, and the Sabbath originally was, dependent upon the lunar cycle. Both date back to the nomadic period of Israel.

Daniel 7:25 in most versions but 5:25 in The Holy Name Version here:
And he shall speak great words against the Most High, and shall wear out the saints of the Most High, and think to change the festivals* and laws: and they shall be given into his hand until a time and times and the dividing of time.
* Heb. Zeman--appointed times-calendar.

Todays Gregorian Calendar
With the assistance of the Italian astronomer Luigi Lilio Ghiraldi and the German Jesuit mathematician Christopher Clavius, Pope Gregory introduced his namesake calendar in 1582.

It was presented before me in the following manner: A large company of heathen idolaters bore a black banner, upon which were figures of the sun, moon, and stars. This company seemed to be very fierce and angry. I was then shown another company bearing a pure white banner, upon which was written, "Purity and holiness unto (YHWH)
Early Writings page 211 & 212

As the storm approaches, a LARGE class who have professed faith in the Third Message, but have not been sanctified through it, abandon their position, AND TAKE REFUGE UNDER THE BANNER OF THE POWERS OF DARKNESS. BY UNITING WITH THE WORLD AND PARTAKING OF ITS SPIRIT, THEY COME TO VIEW MATTERS IN NEARLY THE SAME LIGHT; AND WHEN THE TEST IS BROUGHT, THEY ARE PREPARED TO CHOOSE THE EASY, POPULAR SIDE.
Spirit of Prophecy v. 4, p. 426

The resistance of truth leaves men captive to the will of Satan. Those who today hold fast to erroneous ideas, and feel satisfied with popular errors, rejecting a plain "Thus saith Yahweh," reveal that had they lived in the days of the Messiah, they would have helped to swell the cry of the murderous mob, "Crucify Him! Crucify Him!"
The Paulson Collection of Ellen G. White Letters-page 3, pg. 4

Exodus 12:2
2 This month [shall be] unto you the beginning of months: it [shall be] the first month of the year to you.

Exodus 13:4
4 This day came ye out in the month Abib.