The 1752 Calendar Change

In accordance with a 1750 act of Parliament, England and its colonies changed calendars in 1752. By that time, the discrepancy between a solar year and the Julian Calendar had grown by an additional day, so that the calendar used in England and its colonies was 11 days out-of-sync with the Gregorian Calendar in use in most other parts of Europe. 

England's calendar change included three major components. The Julian Calendar was replaced by the Gregorian Calendar, changing the formula for calculating leap years.  The beginning of the legal new year was moved from March 25 to January 1.  Finally, 11 days were dropped from the month of September 1752. 

The changeover involved a series of steps:

• December 31, 1750 was followed by January 1, 1750 (under the "Old Style" calendar, December was the 10th month and January the 11th)
• March 24, 1750 was followed by March 25, 1751 (March 25 was the first day of the "Old Style" year)
• December 31, 1751 was followed by January 1, 1752 (the switch from March 25 to January 1 as the first day of the year)
• September 2, 1752 was followed by September 14, 1752 (drop of 11 days to conform to the Gregorian calendar)

Source: http://www.cslib.org/CalendarChange.htm