When did equal temperament become widely adopted in France and Germany?

Equal temperament was widely adopted in France and Germany by the late 18th century.1

While the concept of equal temperament was explored by theorists as early as the 16th and 17th centuries—including proposals by Vincenzo Galilei, Zhu Zaiyu, and Marin Mersenne—its practical implementation evolved gradually. German musicians and theorists, notably Andreas Werckmeister in the early 18th century, were among its most effective advocates, and the system was often approximated by organ and harpsichord tuners before its formal widespread adoption.1

By contrast, the system did not see widespread adoption in England until the 19th century.1