The same date conversion rules applied to Ireland as they did Britain.
Some English documents were dated using regnal years; the period by which a ruling monarch served on the throne.
The Internet contains much information about the topic, but few sources present the information properly.
In fact, there is a lot of misinformation on the Web that serves only to confuse the subject even further.
If a date fell between 1 January and 24 March, and between the years 15, it had to be represented with dual years.
To represent a dual year, one year was added to the Julian year.
The fourteenth year references year fourteen of King George IIs reign. Sunday became the first day, Monday, the second day, etc.
It is worth noting that historians do not generally use the Gregorian calendar when recording dates prior to its adoption on 15 October 1582.
In England and its colonies, regnal years were occasionally used as time markers.
1 Henry English and early American documents sometimes include wording such as, the fifteenth of May, in ye fourteenth year of His Majestys reign, George. Prior to 1752, the Religious Society of Friends, more commonly known as Quakers, subscribed to the Julian calendar like the rest of their British counterparts with one exception; they used numbers to denominate the names of the months and days of the week.
Dates can also be represented by adding the notation, Old Style (O. S.), to historical dates for clarification of the calendar system used; Old Style, referencing the Julian calendar and New Style, the Gregorian calendar. However, Scotland changed its New Year to 1 January in 1600, meaning dual year dating was not needed for Scottish dates beginning 1 January 1600.
So, a distinction between the two dating systems would be written: 20 January 1718 O. Like Britain, dual day dating still applied until 14 September 1752.