Imagine having just paid your rent. You have a whole month until you have to pay again. You go to bed secure in that knowledge.
When you wake up the next morning you discover 11 days have been removed from the calendar and your rent will be due again only 20 days!
This is exactly what happened when the Julian Calendar was revised to the Gregorian calendar.
And why was it revised? So that EASTER could be celebrated "correctly".
The last day of the Julian calendar was Thursday, 4 October 1582 and this was followed by the first day of the Gregorian calendar, Friday, 15 October 1582 (the cycle of weekdays was not affected).
So, that was that, eh? All settled? No way! Different countries went about it (or not at all) individually! Each country (Protestant or Catholic) either complied or ignored Pope Gregory's revision.
Depending on where you lived, a letter mailed which ordinarily took a week and a half to reach its destination might suddenly arrive the same day it was sent!
Why would Protestants pay any attention to a Catholic Pope?
Catholics revised to the Gregorian calendar while many Protestants remained with the Julian Calendar!
Great Britain and the colonies in America did not adopt the Gregorian calendar until 1752!
Wednesday, 2 September 1752 was followed by Thursday, 14 September 1752.
What if you were living in Alaska?
In Alaska the change took place when Friday, 6 October 1867 was followed again by Friday, 18 October after the US purchase of Alaska from Russia, which was still on the Julian calendar. Instead of 12 days, only 11 were skipped, and the day of the week was repeated on successive days!
So What?
Think about this.
When Jehovah's Witnesses start computing the "correct" day to observe THE MEMORIAL they do so at the command of a CATHOLIC POPE!
As much as individual nations, tribes and religions have arbitrarily adopted (or not) completely arbitrary means of computing time, days, months and years---How could any reasonable person think it is even possible to know how many years have passed from event to another event?
Keep that upper most in your mind the next time the Watchtower starts mouthing off about dates and times in their cartoon chronology!
It was introduced by Pope Gregory XIII, after whom the calendar was named, by a decree signed on 24 February 1582