Calendar Change left Weekly Cycle Untouched

"Q: What about the calendar change from the Julian to the Gregorian calendar? 

Here are the facts: The Julian calendar had been based upon a year lasting 365.25 days, but this was slightly too long; the real length of a year is closer to 365.2422 days. 

Over the course of twelve centuries, the calendar had drifted increasingly out of alignment with earth’s orbit of the sun; hence things like the summer and winter solstices were, per the calendar, on the wrong day.

Pope Gregory the XIII’s scientific advisers told him he needed to delete 10 days from the calendar to bring it back into alignment with the heavens. Consequently, the pope issued an edict that 10 days would be omitted from the month of October in the year of the Lord (Anno Domini, [A.D.]) 1582. That year, the change to the new calendar was made in most Catholic Spain, Portugal, and Italy. This is why the present calendar is known as the Gregorian calendar.

The way the change was effected 

--was that Thursday, 

--the fourth of October, 

--was followed immediately by Friday, 

--the fifteenth. 

The result was that although 10 days were removed from the month, the order of the days of the week was not interfered with. 

And it is the cycle of the week that measures off the Sabbath day for us.

Not only was the week not tampered with in the revision of the

calendar, but even the idea of breaking the weekly cycle in any way was not thought of. Speaking of the variety of plans suggested for the correction of the calendar, the Catholic Encyclopedia says,
“Every imaginable proposition was made; only one idea was never mentioned, viz., the abandonment of the seven-day week.” - Volume 9, p. 251.

Furthermore, the accurate keeping of time records is a vital necessity in religious worship, both for Christians and for Jews. Christianity and Judaism have come down through all the centuries since Bible times. They are probably the most definite links binding us to ancient times." 

F.D. Nichols
And on the seventh day God ended His work which He had made; and He rested on the seventh day from all His work which He had made. Genesis 2:2