Before 1752 the world used a different calander than it does today. Prior to 1752 the first month of the calander year was March. So, the only dates that need to be translated are before 1752. One of the reasons Friends did not use names for days of the week and months was because they believed the names were Pagan. (more than one God) Check out this website, I use it for my calander issues:
The Quakers didn't change anything they just kept using numbers instead of names, we were the ones who changed. So, you have to keep in mind that before 1752 March was the first month. Before 1752, the safest thing to do is just record the date the way it is written and let others translate. Sometimes you will see a date with 'os' added after the date (old style) to remind the reader that the date must be translated to todays calander. ie: 7mo 11, 1712os translate to Sept. 11, 1712. You add two months to whatever the month number is. The safest thing is to just copy the date like it is written until you understand it a little better.