It's a myth!!
The Gods
It is just a famous myth that most people know.
Theseus and the minotaur.
This is a myth, so the "date" is not much of a realistic answer, because it never existed. However, this myth was written in the mid- 4th century, to the 5th century, when it was revised.( To make it more enhanced) The myth states that "King Theseus" was 'born' into mythology (sentence 2).
Theseus kills a few creatures in Greek myth, but the most famous is the Minotaur.
Minotaur
Greek myth does not say.
He was the son of Poseidon and a mortal woman.
Phaedra of Greek myth had Demophon and Acamas by Theseus.
The Greek Myth, Theseus and the Minotaur.
Most likely the Athenians, as Theseus was their hero/king.