|Pope Gregory IX (1552-1614)|
If this were not a leap year, today or yesterday would have been the vernal equinox, the first day of spring. Instead it was on the 19th. It is a testimony to the accuracy of the Gregorian calendar that the equinoxes and solstices otherwise come on the same dates every year.
The differences between the Gregorian and Julian calendars are so slight that few of us will experience them in our lifetimes. In the Gregorian calendar, century years are not leap years, unless divisible by 400. Then they are. Thus the year 2000 was a leap year in both calendars. 1900 was not and 2100 will not be. In the Julian calendar all were leap years.
The Gregorian calendar reform was adopted by Catholic countries in the 16th Century and by Protestant countries in the 18th Century. Russia, as a Russian Orthodox country, was not interested in reforms promulgated by the Pope of Rome. As a Czarist country they were not interested in reforms.
To this day, Lenin and the Bolsheviki storming the Winter Palace in 1917 is known in Russia as the October Revolution and everywhere else as the November Revolution.