When the world lost 10 days.

Prior to 1582, the world followed the Julian calendar, which was introduced by Julius Caesar, who borrowed it from the Egyptians. But this calendar, assumed one year to be 365.25 days, while in actual a solar year- the time required for the earth to complete an orbit around the sun is 365 days 5 hours 48 minutes and 46 seconds. This is 11 minutes 14 seconds less than 365.25. As a result, dates on the calendar gradually lost their intended relation to solar events and seasons. The vernal equinox which was fixed by the first council of Nicaea, as March 21 was actually occurring on March 11, due to the accumulating inaccuracy of the Julian calendar.

So in 1582, Pope Gregory XIII, introduced the reformed calendar, which we now know as the Gregorian Calendar. To adjust the dates, Pope Gregory ordained that October 4 was to be followed by October 15. The leap years of the old calendar were readjusted and to prevent the accumulation of another 11-minute a year discrepancy, the Gregorian calendar omitted the leap day from years ending in hundreds unless they were divisible by 400. This is the calendar that we still follow.

There was a lot of resentment from many countries, simply because the reform had come from Rome. Protestant England and American colonies refused to go along and they accepted it only in 1752.

Back in 1582, when Pope Gregory took ten days out of the calendar, there had been grumbling and confusion. Servants demanded their usual full monthly pay for the abridged month and employers refused. People objected to their life being shortened by a Papal decree.

In China the revolution of 1911 introduced the Gregorian calendar, alongside the Chinese one. Until well past 1900 Russia used the Julian calendar and lagged to Gregorian calendar by weeks. This lag explains why the “October Revolution” that brought Vladimir Lenin and Bolsheviks to power in 1917 actually occurred in November.