1500 s dating
The European colonies of the Americas adopted the new style calendar when their mother countries did.In what is now the continental United States, the French and Spanish possessions did so before the British colony.For example, in the article "The October (November) Revolution" the Encyclopædia Britannica uses the format of "25 October (7 November, New Style)" to describe the date of the start of the revolution.When this usage is encountered, the British adoption date is not necessarily intended.To reduce misunderstandings about the date, it was normal in parish registers to place a new year heading after 24 March (for example "1661") and another heading at the end of the following December, "1661/62", a form of dual dating to indicate that in the following few weeks the year was 1661 Old Style but 1662 New Style.Some more modern sources, often more academic ones, also use the "1661/62" style for the period between 1 January and 25 March for years before the introduction of the Gregorian calendar in England. Great Britain, Ireland and the British Empire (including much of what is now the eastern part of the United States) adopted the Gregorian calendar in 1752, by which time it was necessary to correct by 11 days.
In England and Wales, Ireland, and the British colonies, the change to the start of the year and the changeover from the Julian calendar occurred in 1752 under the Calendar (New Style) Act 1750.
The Battle of the Boyne in Ireland took place a few months later on 1 July 1690 (Julian calendar).
This maps to 11 July (Gregorian calendar), conveniently close to the Julian date of the subsequent (and more decisive) Battle of Aughrim on 12 July 1691 (Julian).
However confusion occurs when an event involves both.
For example, William III of England arrived at Brixham in England on 5 November (Julian calendar), after setting sail from the Netherlands on 11 November (Gregorian calendar), in 1688.