If you lived in London or Philadelphia in 1752, you went to bed on Wednesday, September 2, and woke up on Thursday, September 14. Eleven days simply did not happen. Nobody lost any time, of course. The calendar changed, not the sun. But the jump left a puzzle that still trips up anyone reading old documents, and it is one of the best examples of why "on this day in history" is more complicated than it looks.
Two calendars
For centuries, much of Europe used the Julian calendar, introduced under Julius Caesar in 46 BC. It added a leap day every four years, which made the average year 365.25 days long. The real solar year is slightly shorter, about 365.2422 days. The difference is small, about 11 minutes a year, but over centuries it adds up. By the 1500s, the calendar had drifted about ten days out of line with the seasons, which affected the calculation of Easter.
In 1582, Pope Gregory XIII issued a papal bull introducing a reformed calendar. The Gregorian calendar dropped ten days at once and changed the leap year rule: century years are leap years only if divisible by 400. So 1600 and 2000 were leap years, but 1700, 1800 and 1900 were not. Catholic countries such as Spain, Portugal and the Italian states adopted it in 1582. Many Protestant and Orthodox countries did not, at least not right away.
Britain's late switch
Britain and its colonies, including the American colonies, kept the Julian calendar for another 170 years. By the 1700s, the gap had grown to eleven days.
Parliament finally passed the Calendar (New Style) Act in 1750, often called Chesterfield's Act after Lord Chesterfield, who championed it. The act set the switch for 1752. To bring the calendar back in line, September 2, 1752, was followed directly by September 14.
The same act also changed the start of the legal year. Under the old system in England, the legal year began on March 25, Lady Day. So a date in February could be written as 1750 by some and 1751 by others. From 1752, the year officially started on January 1.
The riots that probably weren't
A popular story claims that crowds rioted in the streets demanding "Give us our eleven days!" The story appears in many retellings. Historians have found little contemporary evidence for actual riots over the calendar change. The phrase may come partly from a 1755 William Hogarth painting, An Election Entertainment, which shows a placard reading "Give us our Eleven Days," as part of a satire on election politics. The story of mass riots is now widely considered an exaggeration or myth.
That is a good lesson for anyone reading history online. A vivid story repeated many times is not the same as a documented event.
Old Style and New Style
Because of the change, historians often mark dates from this period as Old Style (O.S.) or New Style (N.S.). Old Style means the Julian calendar. New Style means the Gregorian.
The most famous example is George Washington's birthday. He was born on February 11, 1731, according to the Julian calendar then in use in Virginia. Under the Gregorian calendar, and with the year starting January 1, that date becomes February 22, 1732. Washington himself came to celebrate the later date.
Other examples show up all over history. Events in Britain before 1752 and in Russia before 1918 often have two dates, depending on which calendar a writer used. Russia's October Revolution in 1917 took place in November by the Gregorian calendar, because Russia was still using the Julian calendar at the time.
Why it matters for "on this day"
This is where anniversary lists can go wrong. Should we remember an event from 1700 in London on the date written at the time, or on the equivalent Gregorian date? Different sources make different choices, and many do not say which they chose.
If you see two different dates for the same event, check:
- Where did it happen? Countries switched calendars at different times. Some German Protestant states switched in 1700, Britain in 1752, Japan adopted the Gregorian calendar in 1873, Russia in 1918 and Greece in 1923.
- When did it happen? Anything before a country's switch may be recorded in Old Style.
- What year convention is used? Dates between January 1 and March 24 in England before 1752 can have a year that differs by one, depending on the source. You may see them written as "1750/51."
Good sources often state the calendar explicitly. When they do not, it is worth a second look.
The calendar is still a compromise
Even the Gregorian calendar is not perfect. Its average year is still slightly longer than the solar year, by about 26 seconds. That works out to an error of about one day every several thousand years. Nobody is planning to skip days again anytime soon.
So the next time you see a date from the 1700s, remember the people who went to bed on September 2 and woke up on September 14. They did not lose eleven days of their lives. But they did leave historians a puzzle, and a lesson that dates are always a matter of agreement as well as fact.