The adjective archaic means belonging to an ancient era in history.
Synonyms are ancient, antique, obsolete, or primitive.
The word origins from French (1810) archaique ultimately, from Greek arkhaikos meaning “ancient, old-fashioned, antiquated, primitive”, and from arkhē meaning “beginning, origin”.
The ritual is obviously very archaic.
He presents archaic tools to his friends.
He has archaic ideas about pregnant women.