Up until 1752, Great Britain and America followed the Julian calendar, which is the Roman calendar Julius Caesar initially set into motion. A competing Gregorian calendar was created by Pope Gregory the XIII in 1582. Many countries got on board at that time. Great Britain and America did not adopt the Gregorian calendar until many years later.
There is an 11-day gap between the Julian calendar and the Gregorian calendar. When the Gregorian calendar is adopted, 11 days from the Julian calendar must be dropped.
George Washington was born under the Julian calendar. After America adopted the Gregorian calendar, Washington’s birthday moved from February 12 to February 22.
George Washington was well loved and admired for leading America through the Revolution and serving as our first President. After his death, his “new” birth date, February 22, 1732, was observed as a national holiday.