Calendar changes 1752
In 46 BC Julius Ceaser fixed the length of a year at 365 days, and 366 days every fourth year. He fixed the months at 30 & 31 days alternatively, with the exception of February (then the last month of the year) having 29 days in ordinary years and 30 in leap years. To mark this July was named after its originator.
The Julian calendar made a slight error in the length of a year (11 minutes 14 seconds). By the sixteenth century the cumulative error was about 10 days. Pope Gregory XIII rectified this in 1582 by decreeing that the 5th October become the 15th October and to stop it happening again it was ordained that the centurial years (i.e. 1600, 1700 etc) should not be leap years unless divisible by 400.
England did not accept this Gregorian calendar until 1752, thereby causing a lot of confusion between English and continental dates.
An Act of Parliament in 1750 made 2nd September 1752 into 14th September 1752 causing the residents of Cocker Hill (and the rest of England) to time travel 12 days into the future The Act also changed the start date of the new year to January.
Before 1752 the new-year began on 25th March. Ie 24th March 1700 was followed by 25th March 1701 etc. and 31st December 1700 was followed by 1st January 1700. Confusing? I thought so too, as when looking at old dates I automatically assume that January of a particular year came before December of the same year.
Cocker Hill, Stalybridge 
25th March was Lady Day. We still run our tax years on that principle, because we begin our tax years on 5th April. This was to avoid having a short year with ten fewer days for tax collection and playing havoc with the books. Among the last countries to adopt the new calendar was Russia. Perhaps it has something to do with the orthodox church. This is why the October revolution (of 1917) took place in november. Officially it was november, but the public were still using the old calendar.
Thanks Steve, great info I didn’t know either of those. I like now knowing the background to tax years – I’ve worked in Finance for 20 years and never figured why the tax year end was April.