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.

Ezekiel 46:1  Thus saith Yahweh; 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.
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 Yahweh.

Looking down from above the solar plane, the earth and moon orbit the sun. Tracking orbital motion, the point tip is the moon, almost still in relative space. Moon is at transitional point as the earth travels past, the moon is pulled from the suns gravity, which had accelerated its speed, as it had traveled toward the sun. Breaking away from the sun's pull, the moon begins to travel from the sun, accelerating on to orbit the earth again. As it begins moving in relative space, in a new direction, away from the sun, the new moon shows a sliver of light.

						Moon Av
2005 E.D.T.					Day of the New Moon Emerging from sleep	1 0% July 06 Wed 8:30pm
						July 07 Thu
1st day	2nd day	3rd day	4th day	5th day	6th day	7th day Sabbath
22% July 07 Thu 8:30pm	35% July 08 Fri 8:30pm	410% July 09 Sat 8:30pm	517% July 10 Sun 8:30pm	625% July 11 Mon 8:30pm	734% July 12 Tue 8:30pm	843% July 13 Wed 8:30pm
July 08 Fri	July 09 Sat	July 10 Sun	July 11 Mon	July 12 Tue	July 13 Wed	July 14Thu
954% July 14 Thu 8:30pm	1064% July 15 Fri 8:30pm	1174% July 16 Sat 8:30pm	1283% July 17 Sun 8:30pm	1391% July 18 Mon 8:30pm	1496 July 19 Tue 8:30pm	1599% July 20 Wed 8:30pm
July 15 Fri	July 16 Sat	July 17 Sun	July 18 Mon	July 19 Tue	July 20 Wed	July 21 Thu
1699% July 21Thu 8:30pm	1796% July 22 Fri 8:30pm	1890% July 23 Sat 8:30pm	1982% July 24 Sun 8:30pm	2072% July 25 Mon 8:30pm	2161% July 26 Tue 8:30pm	2251% July 27 Wed 8:30pm
July 22 Fri	July 23 Sat	July 24 Sun	July 25 Mon	July 26 Tue	July 27 Wed	July 28 Thu
2340% July 28 Thu 8:30pm	2431% July 29 Fri 8:30pm	2522% July 30 Sat 8:30pm	2614% July 31 Sun 8:30pm	278% Aug 01 Mon 8:30pm	284% Aug 02 Tue 8:30pm	291% Aug 03 Wed 8:30pm
July 29 Fri	July 30 Sat	July 31 Sun	Aug 01 Mon	Aug 02 Tue	Aug 03 Wed	Aug 04 Thu
				Moon  at transition point	Not a 7th day Sabbath	300% Aug 04 Thu 8:30pm
						Aug 05 Fri

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.