Today is the 253rd anniversary of Britain's conversion from the Julian Calendar to the Gregorian Calendar (British territories such as North America changed too).
If this was 1752 yesterday would have been 2nd September, today would be 14th. So if you had been looking forward to any dates from 03/09/52 to 13/09/52 you were to be disappointed.
The Julian calendar is usually referred to as OS (Old Style) with the Gregorian as NS (New Style), how does this relate to coins you ask?
Well up until 1752 the new year did not begin on 1st Jan but rather on the 25th of the third. The new year began with spring.
Towards the end of 1701 (this being the end of Feb and upto mid march) the Royal mint had begun producing William III fourpence coins dated 1702. Unfortunately for the mint and for William he died on the 8th of the third 1701 some 17 days short of the new year.
So whilst to contemporaries William had died in the closing days of 1701 and thus the fourpence coins were issued bearing a date that the king had never lived in, after 1752 with the adoption of the Gregorian calendar, historians went and changed all the dates. Events occuring between Jan 1st and 24th Mar now happened the following year. So William's date of death is now considered to be 8th March 1702, despite the fact that in his time that was a whole year later.*
Fascinating no?
*I should point out that there is a major difference between the US and British traditions in showing these dates between the two calenders. The US usually alters the date itself by adding on (i think) those missing 11 days. Although the amount of missing days depends upon the century, there's less the further back you go) So 8th March 1701 would be 19th March 1702 from a US perspective. Britain however leaves the dates in their Julian context and merely changes the year. Why i don't know, but it makes it easier for figuring out the dates between the two.
Henry VIII died in 1546 OS (not 47), Charles I was beheaded in 1648 OS (not 49).