To understand the dates in the past as they compare today, it is necessary to understand the changes made when calendars switched from the Julian calendar to the Gregorian calendar. In 1582, the Gregorian calendar was decreed to take effect the day after Oct. 4, 1582, becoming Oct. 15^th instead of Oct. 5^th.

The Gregorian calendar was immediately put into use by France, Italy, Spain, Portugal and Luxembourg. The German Catholic States, Belgium, parts of Switzerland and the Netherlands began to use it within two years. Hungary in 1587. The rest of the Netherlands, Denmark, and the German Protestant states changed in 1699-1700.

In 1752, the British Government began using the Gregorian calendar in its possessions, including the American colonies. It was decreed that the day following Sept. 2, 1752, should be called Sept. 14, a loss of 11 days. All dates preceding were marked O. S., for Old Style. In addition New Year’s Day was moved to Jan. 1 from Mar. 25 (e.g., under the old reckoning, Mar. 24, 1700 had been followed by Mar.25, 1701.) George Washington’s birth date, which was Feb. 11, 1731, O. S., became Feb. 22, 1732, N. S. (New Style.)

Other countries didn’t change until the 1800’s, even 1900’s. Greece was the last to do so in 1923. For the first time in history, all major cultures have one calendar. (The Russian Orthodox Church and various Middle Eastern Christian Sects still use the Julian Calendar.)

To change from the Julian calendar to the Gregorian calendar, add 10 days to dates Oct. 5, 1582, through Feb. 28, 1700; after that date add 11 days through Feb. 28, 1800; 12 days through Feb. 28, 1900; and 13 days through Feb. 28, 2100.

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This information was transcribed from the 1993 World Almanac for educational purposes with some changes to the text.