The 1752 calendar change Before 1752, the year number changed over on March 26th. 1752 was the first year that January 1st was the first day of the year. This gives us a potential little problem when recording dates before March 26th in each year. If March 26th was the first day of the year, and let's say a couple were married on that day, in 1750. That's our problem.
Some genealogists record precisely what is recorded in a parish register.
Some record it as written, but didn't realise that in our modern calendar they could actually be referring to a different year. It is them extremely obvious that 1750 is what was written in the register, but it was really 1751 in the new calendar. So, for all years up to and including 1751, dates between 1 January and 25 March inclusive, are written with double dates. Regnal years Regnal years are really hard to get to grips with. Unfortunately, some clergymen used them in earlier registers.