Why 11 days vanished in 1752

People in Britain went to bed on Wednesday 2 September 1752 and woke up on Thursday 14 September. Here's why, and how that strange week still shapes British life today.

A calendar that had drifted

Britain was still using the Julian calendar, set up under Julius Caesar. Its leap year every four years makes the average year about 11 minutes too long. Over the centuries those minutes piled up, and the calendar slowly slipped out of step with the sun and the seasons.

In 1582 Pope Gregory XIII fixed this for Catholic Europe by dropping ten days and changing the leap year rule. Protestant Britain refused to follow a reform from Rome, and for 170 years Britain and much of the Continent were on different dates. By 1752 the gap was eleven days.

The Calendar Act

The Calendar (New Style) Act 1750, often called Chesterfield's Act after the peer who championed it, made two changes:

• New Year's Day moved to 1 January. The legal year in England had begun on 25 March, Lady Day. So the year 1751 began on 25 March and ended on 31 December, making it only 282 days long.
• Eleven days were dropped in September 1752, and the Gregorian leap year rule was adopted from then on.

The days of the week carried on as normal: Wednesday 2nd was followed by Thursday 14th.

Did people riot?

The story that crowds rioted shouting “Give us our eleven days!” is very probably a myth. There's little evidence of real riots. The slogan is best known from a William Hogarth painting of an election in 1755, where it appears on a placard. People were understandably confused about rents, wages and birthdays, though, and the Act included rules so that rents, wages and interest fell due after the same number of real days, so nobody paid for days that never happened.

Why the UK tax year starts on 6 April

Quarter days like Lady Day (25 March) were when rents and taxes fell due. To avoid collecting a full year's tax for a year that was 11 days short, the Treasury moved the end of its year on by 11 days, to 5 April. When 1800 was not a leap year under the new rules but would have been under the old, the start shifted one more day, to 6 April, where the UK tax year still begins.

What it means for historians

Any English date before September 1752 is an Old Style date. Dates from 1 January to 24 March were often written with two years, such as 1731/2, because they fell in the old legal year but the new historical one. If you're reading parish registers, wills or letters from before 1752, the Old Style to New Style converter and the day of the week calculator will save you a lot of head-scratching.