I was reading Thomas Jefferson's Wikipedia page and noticed that there is a second date listed as his birthday. If they quit using O.S. In the 16th century why is it relevant to Jefferson?
The dates changed in 1752 due to the Calendar Act of 1752. So Jefferson, Ben Franklin, and others born before 1752 would have a O.S. birthdate and after the change they would have a N.S. birth date.
https://en.wikipedia.org/wiki/Calendar_%28New_Style%29_Act_1750