That's why the calendar goes from Thursday, October 4 to Friday, October 15 in 1582. It effectively erased 10 days from history but it's so the vernal equinox could be reset to March 21. Catholic ...

When the Julian calendar was brought into effect ... and that is why, in 1582, October 4 was followed by October 15. Moreover, a reform was carried out in the lunar cycle used to calculate the ...