Frankfurt adopted the Gregorian calendar in 1700.
When Frankfurt adopted the Gregorian calendar in 1700, the new date of the Frankfurt fair conflicted with the date of the Leipzig fair.
- Carlbach, Elisheva. Palaces of Time. Harvard University Press, 2011.
This is part of a general wave of adoption by protestant Germany in the same year. The calendar had been made more palpable to the Lutheran princes because this time it was a slightly modified form, as proposed by Erhard Weigel.
In 1700, the protestants of the empire generally abandoned the old calendar and adopted a new one, framed by a celebrated mathematician named Weigel, which differed only from the Gregorian as to the mode of fixing Easter and the Movable feasts.
- Nicolas, Nicholas Harris. The Chronology of History: Containing Tables, Calculations & Statements Indispensable for Ascertaining the Dates of Historical Events and of Public and Private Documents from the Earliest Periods to the Present Times. Longman, Brown, Green and Longman's and John. Taylor, 1838.
Scandinavia, Switzerland and the Low Countries adopted the Gregorian calendar at the same time.