On 14 September 1752, Britain began using the Gregorian calendar. The previous day had been Wednesday, 2 September. Thursday was dated 14 September, removing eleven dates from the British calendar.

Nobody actually lost eleven days. Time continued normally from Wednesday to Thursday. The dates 3 to 13 September disappeared.

Britain had continued to use the Julian calendar long after much of Europe had changed to the Gregorian system. Pope Gregory XIII introduced the Gregorian calendar in 1582 to correct an accumulating error in the older calendar.

The Julian system treated every fourth year as a leap year. This made its average year slightly longer than the solar year. The difference was small, but accumulated over centuries. By the eighteenth century, Britain was eleven days behind countries using the Gregorian calendar.

Parliament dealt with the problem through the Calendar (New Style) Act. The legislation ordered that 2 September 1752 should be followed by 14 September, bringing British dates into line with the Gregorian system.

The reform made another important change. In England, the legal or civil year had previously begun on 25 March. However, people already treated 1 January as New Year’s Day. Under the new system, the civil year began on 1 January.

The change applied to Great Britain and its colonies, so its effects extended well beyond Britain.

Stories that angry crowds demanded ‘Give us our eleven days’ became part of the popular account of the reform. Evidence for widespread calendar riots is uncertain, however, and the story should not be treated as a straightforward record of what happened.

From 14 September 1752, British officials used the Gregorian calendar.