Old Style and New Style Dates
And the change to the Gregorian Calendar in 1752
Dates before 1752 hold a nasty trap for the unwary family historian as the year number did not change until Lady Day, 25th March. So, for instance, 31 December 1722 was followed by 1 January 1722 and 24 March 1722 was followed by 25 March 1723. This can lead to the situation where a couple could be recorded as marrying in April 1722 and their first child being baptised in February 1722, which looks to the unwary researcher as though the child was born before the marriage when in fact it was probably well after.
Researchers who study original parish registers are less likely to fall into this trap as the change of year number is usually clearly marked in the register, but with more and more researchers using indexes it can cause confusion. It can also be a problem when writing histories such as the pages on this website. Consequently it is a common practice to indicate these problematical dates by showing both year numbers. So the baptism referred to above could be shown as occurring in February 1722/3 to indicate that the register says 1722 but by the modern calendar we would think of it as 1723.
In Britain the Calendar (New Style) Act of 1750 was passed to change the date on which the year number changed to 1st January, and also to convert from the Julian to the more accurate Gregorian calendar. Because the Julian calendar, introduced by Julius Caesar, had a leap year every 4 years the calendar had, over many centuries, got out of step with the seasons. The Gregorian calendar, introduced by Pope Gregory XIII corrected this by not having a leap year in century years (1800, 1900 etc.) unless the century year was divisible by 400 (eg. 2000).
Consequently 1751 was a short year, beginning on 25th March and ending on 31st December. 1752 then began on 1st January and later that year a correction was applied, to bring the calendar back into line with the seasons, by removing 11 days. Wednesday, 2 September 1752 was followed by Thursday, 14 September 1752.
The problem with the change of calendar is even more complicated when you remember that it was first proposed in 1582 and many catholic countries, including France, adopted it then or shortly after. However, the protestant countries of Northern Europe were slower to convert, and did not all convert at once, leading to the situation that documents in different countries can refer to the same event on different dates simply by the use of different calendars. Britain and the British Empire was relatively late, converting in 1752, although Scotland had already adopted the January start date in 1600. Some countries, including China, did not adopt the new calendar until well into the twentieth century. Even before the change in Britain some documents did use the new style year causing even more potential confusion for researchers.