The Ancient Church of the East began when in 1968 some members of the Assyrian Church of the East - at the time led by Shimun XXIII Eshai - left it and consecrated their own patriarch, Thoma Darmo. Darmo was strongly opposed the system of hereditary succession of the position of patriarch of the Assyrian Church of the East, as well as the latter's adoption of the Gregorian calendar "and other modernizing masures".