Ben Franklin was born on January 6–and on January 17! His birth date is recorded as January 6, 1706, in the baptismal records of Old South Church in Boston, as well as in the city’s Registry of Births. Today, however, we celebrate Franklin’s birthday as January 17, thanks to the Gregorian calendar. Until 1752, the Julian calendar was in effect in England and the colonies. When the Gregorian calendar was adopted, bringing the calendar year in line with the astronomical year, 11 days had to be add