When I started out on my own genealogical project, I began by entering all of my grandmother's meticulous research into my genealogy software. Encountering dates such as 12 da, 4mo 1660, I blithely entered them into my computer as April 12, 1600! Fortunately for me, one of my first correspondents - Cheska Wheatley - happens to be an expert on Quaker genealogy and she quickly set me straight. The following is what I received from her, and I've found it to be very clear and useful!
"OUR QUAKER ANCESTORSFrom Chapter VII "Quaker Records and Some Possible Problems" pg.67 and 68:
Finding Them in Quaker Records"
by Ellen Thomas Berry & David Allen Berry
"Another pitfall for the purist can be the unique way the Quakers dated events. They did not use names for days of the week or months of the year since most of these names were derived from the names of pagan gods. A date such as August 19, 1748 will never be found. Rather it would be written as "19th da 6th mo 1748." Sometimes this will be written as 6mo 19da 1748. Why 6th month since August is the 8th month? The Quakers, along with everyone else in the American Colonies and England, did not begin using the Gregorian calendar until 1752. Under the Julian calendar the year began on March 25th; March was the first month and February was the twelfth month. This is something of a problem when an event occurred in the months of January, February or up to March 25th, for then the date is given as 1748/1749. Such a dating practice satisfied everyone, including civil authorities, if for instance an inheritance was being established.
You may find that some legal documents will read "the 8th mo 5th day 1748 in the month called October." It is disconcerting when a date such as 30th da 11th mo 1722/1723 is found. The double year indicates that the old calendar was in use. Even though the Gregorian Calendar was adopted in 1582, as mentioned above it was 1752 before the change was universally accepted. We are emphasizing this point here so that if exact days, months, and years are wanted, the old Quaker records must be used with great caution. Remember that until 1752 "1st mo" is March.
We would like to point out also that you may find secondary material (genealogies are a case in point) in which the compiler transcribed dates incorrectly - for instance. "30th da 11th mo 1738/1739" rewritten as "Nov. 30, 1738/39" when the date in question is actually "30th January 1738/1739. The dual year must be used until you are quite certain the locale in question has adopted the Gregorian calendar (or until the Quaker records no longer have the dual form or the year is after 1752). Dual dating is applicable ONLY for the first three months (to 25 March) of the present calendar and NOT for the other nine months. The first date given is the Julian year, the second the Gregorian year."
Another way of finding whether the old Quaker method of dating is being used in any given set of records is to search back and forth until a month such as the "2nd mo" is found and the see if entries were made on either the 29th or 30th days, If this was done, then you will know the old system was being used and the month would be the present month of April rather than February. Other months can be used. For instance, if it is the "7th mo" and you find the "31st," you would know the new system is being used and the month is our present month of July rather than the Quaker September."
In other words, before 1752, 11th month was January; 12th month was February; 1st month was March; 2nd month was April and so on.
1752 and after, 1st month was January, 2nd month was February, 3rd month was March...just as we number the months today.
When recording dates found in Quaker records, it is preferred practice to copy them as they are found and to record the source. Too often, dates have been transformed incorrectly in secondary sources and these dates should always be verified by the original monthly meeting records.
If you are using a commercial data base which does not permit entry of dates which reflect the manner in which they are found in the original records, I recommend putting only the year in the date field. In the next field where you would ordinarily enter the name of a city or township, enter the date again but as it was found. This can be followed by the name of the Monthly Meeting where the date was recorded, followed by the State.
When you print a family group sheet or other chart your output may look like this:
b. 1743 2 3m 1743 New Garden MM, NC
d. 1755 3 1m 1755 Deep River MM, NC
bur. 1755 5 1m 1755 Deep River FBG, NC
b. 1745/46 4 1m 1745/6 New Garden, MM, NC.
This may seem redundant, but to the recipient of your chart, it will be abundantly clear that your source came from an original church record and was not copied from the IGI or Ancestral File which are notorious for incorrectly recording this type of date.