<!doctype html public «-//w3c//dtd html 4.0 transitional//en»> http-equiv=content-type content="text/html; charset=iso-8859–1"> The Gregorian calendar was introduced in 1582, but at first, this papal reform was only implemented in Catholic areas. Until the 18th century, Catholics and Protestants fought over the correct time and dated events by different calendars. This study examines reactions to the reform and efforts to unify the calendar, offering insights into inter-confessional relations in Germany during the early modern era.