Dating an event according to both the Julian and the Gregorian calendars. During 1752, Great Britain and her colonies officially replaced the Julian calendar, with 25 March as the beginning of the year, by the Gregorian calendar, with 1 January as the beginning of the year. The difference between the two calendars having increased from 10 days in 1582 to 11 days, the change was made by having 2 September 1752, followed immediately by 14 September 1752. To avoid confusion, dates according to the Julian calendar were marked old style or (O. S. ); dates according to the Gregorian calendar were marked new style or (N. S. ). In double dating early American records, not only the day and the month but also the year are subject to change. In England, at the time of the change, the official year commenced on 25 March, so that 24 March 1730 (O. S. ), corresponded to 4 April 1731 (N. S. ), but the next day was 25 March 1731 (O. S. ), or 5 April 1731 (N. S. ). This practise was not universal, for there was some popular use of 1 January as the beginning of the year even before the official change.