Though Catholic countries switched to the Gregorian calendar in the sixteenth century, Protestant countries, such as England and its colonies, refused to switch from the Julian to the Gregorian calendar at that time. It wasn’t until 1752 that Britain and its colonies, including the colonies that soon thereafter became the United States, switched to the Gregorian calendar. By that time, there was an 11-day difference in time, so September 3, 1752, became September 14, 1752.