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.
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.
Therefore, dual dating does not apply before 15 October 1582.
The leap year correction meant that up until Britain adopted the Gregorian calendar on 14 September 1752, additional days had to be added to each recorded date.
The proper number of added days depended on the year.
The following diagram illustrates the number of days to be added when converting from Julian to Gregorian calendar dates: When converting from the Julian to the Gregorian calendar, the date, 11 June 1690, would be 21 June 1690.
10 days are added because there is a difference of 10 days for the year 1690.
When dual dating, two adjustments occur: the day of the month and the year.
When the Gregorian calendar was created in 1582, it was realized that the Julian calendar was 10 days out of synch with the solar year.
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.