This is another source of confusion that I'd like to clarify before too many records get errantly changed.
As the Society of Friends was in its early days mostly an English movement (that later spread to other countries), it becomes vital for anyone reading their records to understand that the English calendar was actually rather late in changing over from Julian to Gregorian calendar. Mostly this was seen as a resistance to "Popish innovations" that were readily accepted in Catholic countries, in accordance with Pope Gregory's decree.
In 1751, Parliament finally gave in to foreign business pressure, and the calendar was at long last adjusted to Gregorian under the Chesterfield Act. This shifted the dates 11 days forward, so that the day after September 2, 1752, became September 14, 1752. (As a result, you can be assured that any event date for England marked September 3-13 is in fact wrong.) But more importantly, the Act shifted New Years Day for 1752 from Lady Day (March 25) to January 1, matching pretty much the rest of Europe.
Where this is important for Quaker calendars is the fact that the Quakers early on regarded the traditional month names (January, February, etc.) as a holdover from Pagan times, and therefore not pleasing to God. So, they used "1mo, 2mo" instead.
Problem is, before 1752, 1mo corresponded to March.
So, if you are dealing with original records showing 1mo or 2mo etc before 1752, and 1mo or 2mo after 1752, realize that these are different months. Before 1752, this would be March or April. After 1752, this would be January or February.
As such, when you see that there are two conflicting dates two months apart, you can be reasonably assured that the later variation is probably correct, if you are dealing with pre-1752 dates. Naturally, you'd want to verify the original recorded date (1mo, 2mo) before conversion (March, April).
There are lots of other Calendar nuances, but this is the major one for Quakers.
* Born "2 mo 2 & 3rd of the week 1723" - so old system which = April 2, 1723.
* Died "1mo 17, 1771 aged 47 years 8 months & 14 days." - so new system = January 17, 1771
* But, calculation does not add up! 47 years 8 months & 14 days would be December 16, 1771
Am I making the mistake? Or did the original writer make one? (see source in profile)