For categories such as Category:1956 establishments by continent, enter:
((Estcatbycontinent))
No parameters are needed.
Note that such "by continent" categories for years before 1500 are deprecated, see Wikipedia:Categories_for_discussion/Log/2017_November_10#Medieval_years_by_continent.
For categories such as Category:1956 establishments in Europe, do not use this template, but ((EstcatContinent)).