Two changes, not one
When Britain adopted the New Style calendar in 1752 it changed two things at once:
- The new year moved to 1 January. Before this, the legal year in England, Wales, Ireland and the colonies began on 25 March (Lady Day). So 24 March 1700 was followed by 25 March 1701, and a date in February 1700 came after one in December 1700.
- Eleven days were dropped. Wednesday 2 September 1752 was followed by Thursday 14 September, bringing Britain into line with the Gregorian calendar used across most of Europe.
That is why so many pre-1752 dates are written with two years. “18 February 1749/50” means the legal year 1749 but the year we would call 1750.
Famous examples
| As written | Double dated | New Style | Event |
|---|---|---|---|
| 11 February 1731 | 11 February 1731/2 | 22 February 1732 | George Washington's birthday |
| 25 December 1642 | 25 December 1642 | 4 January 1643 | Isaac Newton's birth |
| 30 January 1648 | 30 January 1648/9 | 9 February 1649 | Execution of Charles I |
| 18 February 1749 | 18 February 1749/50 | 1 March 1750 | A typical parish register entry |
Should I convert dates in my family tree?
Most genealogists keep the date exactly as the record gives it and add the double year for January to 24 March, for example “3 March 1719/20”. Converting the day and month to New Style is usually only done when comparing English events with those in countries that had already switched, such as France, where 1 March 1720 in England was already 12 March.
Common questions
What is an Old Style date?
A date in the Julian calendar, as used in Britain until 2 September 1752. In England the Old Style year also began on 25 March rather than 1 January.
What does 1749/50 mean?
It's a double date for a day between 1 January and 24 March. The first number is the legal year of the time; the second is the year as we count it today.
How many days do I add to convert Old Style to New Style?
10 days for dates from 1582 to February 1700, 11 days from March 1700 to 1752. The converter works this out automatically.
Did Scotland use 25 March?
No. Scotland moved its new year to 1 January in 1600, but kept the Julian calendar until 1752 like the rest of Britain.