Why Britain skipped 11 days in September 1752

Britain skipped eleven days in 1752 to switch from the Julian to the Gregorian calendar: Wednesday, 2 September was followed directly by Thursday, 14 September. By law, 3 to 13 September 1752 never happened in Britain or its colonies.

The Julian calendar assumed a year of exactly 365.25 days, slightly longer than the true solar year. Over the centuries that small surplus added up, and earlier attempts to adopt the Gregorian fix had failed because the Church of England denounced it as popish.

From papal reform to the tax year

• 1582: Pope Gregory XIII introduces the Gregorian calendar, which most of Europe was using by 1750.
• 1750: Britain is now eleven days out of step. Pushed by George Parker, Earl of Macclesfield, an astronomer helped by the astronomer royal James Bradley, Lord Chesterfield steers the Calendar (New Style) Act 1750 through Parliament. It also moves New Year’s Day from 25 March to 1 January and adopts the rule that century years are leap years only when divisible by 400.
• 1752: the eleven days vanish, but the Act keeps payments of rent and annuities, deliveries of goods, leases and coming of age at 21 to their true natural day, so nobody gains or loses eleven days’ money.
• 1754: “Give us our eleven days” is documented as an election cry in Oxfordshire against Macclesfield’s son.
• 1800: a leap-year mismatch shifts the start of the tax year to 6 April, where the UK tax year still starts. It had begun on Lady Day, 25 March, and had already moved eleven days to early April to keep a full year’s tax.

The famous calendar riots are the weakest part of the story. Tales of mobs chanting for their lost days have little solid evidence behind them, and the legend may come from a misreading of Hogarth’s painting of those 1754 elections. Most historians now treat the riots as an urban myth.