... And if so, why? This query arises from the Family Historian Users mailing list where someone found a reference in a parish register to 29 February 1743, which, after double checking, was clearly 29 February 1743 OS / 1744 NS. Now, 29 February 1743 (the form as written) didn't seem like a valid date at first until someone said it's 29 February 1743 OS / 1744 NS and it certainly would be a valid Leap Year in 1744 NS. Which made sense to me for all of 30 seconds until I asked myself the question - What's a New Style date got to do with it? Surely the effective calendar for identifying Leap Years in England was the pre-1752 Julian calendar when it would be Feb 1743, not divisible by 4 and therefore not a Leap Year? As one of the list members said, "It is not very scientific, but a Google search for 29 Feb 1743 finds lots of entries and many of them use 29 Feb 1743/44 format." I checked this and am looking at a Googled entry for a Nottingham University catalogue entry referring to a "Quit claim in respect of the portion of Isabella Countess of Carlisle charged upon the Byron estate in Nottinghamshire; 29 Feb. 1743/4". So it's used in England. Can anyone say what's going on? Was 29 Feb 1743/44 a Leap Year Day? And why? For instance, did the definition of a Leap Year move to using a New Year starting on 1 January earlier than 1752? Is the answer the same in Scotland as in England? (I just have this vague idea that Scotland moved to a 1 Jan date for New Year before England - if so it would have been inconvenient to have had the 2 Kingdoms 1 day apart for 25% of the time, between their two Leap Years) Thanks for any clarity Adrian B