Genealogy.com has a page explaining the system for Quaker dates . http://www.genealogy.com/rhonda101900.html?priority=0000900 "While you may find it confusing to know when to include the double dating, imagine your frustration when trying to figure out just what the date was when working with Quaker dates. In regular dates, the double dating is usually included for the months of January and February and then March up to the 25th day. Seems simple enough...". (more explanation If you can't get in this way through the address go through http://abcgenealogy.com/New/29-Nov-2004.html and choose "Just when was the first month"... these sites do not require any subscription fee