What comes after Thursday? Thursday!!!

It was a very cold Christmas day of the year 1582 and Pope Gregory XIII was talking to Christopher Clavius, a Jesuist who was very upset at that moment:
«Oh, please, Your Holiness, let me explain the changes in the calendar to the people,» said Christoper.

«Some people have even accused us of stealing 10 days!» Pope Gregory XIII looked at him and said:
«These people are ignorant! The council of wise men determined that our calculations regarding the duration of one year were wrong, because a year is 365 days and a few hours.
We got those days back from the past calendar! If we had continued with the old calendar, we would end up celebrating Christmas in summer!»
So, our calendar was 10 days behind! That`s why the day after 4th October 1582 was 15th October but we didn`t steal those days.

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