When was it that the cults of Selene and Artemis were merged?

Question

Artemis wasn't originally the goddess of the moon, and according to a book I have, there was a merging of thei cults in ancient Greece because Selene-worshippers' numbers kept dwindling. When were the cults merged?

Answer 1

I don't know if there is an exact year, but there is a quote from the Iliad of Homer in roughly 390AD
"Chrysippus in his Old Physics, shows that Artemis is Selene and credits it with an influence on childbirth, says that at the full moon not only do women have the easiest labour but all animals have an easy birth."

Answer 2

Hello dear!
Quite a question! You put me to think!
Well, the twins, Apollo and Artemis, are simultaneously God of the Sun and Goddess of Selene!
Though, these were, exactly cults, for the masses, since the philosophers know that the goddesses and gods are short of speak "names" for the planets, stars, galaxies, phenomena, etc.! Making this mythology, even difficult meanings could pass to all people! Thus, we have "doulos" (not citizens - people with lesser paedeia) who know the signs on the sky, names of planets, seasons and influence of all those to the climate and advice to people for harvesting and other agricultural works!
People tend to understand black or white, not gray! Thus, since Apollo is the Sun, his sister, should be the one next to the Sun, and for people, this is nothing else than the Moon, Selene!
When was that?
Well, it goes back into the times before written History, Mythology! I would place it around the Mycenaean times, Copper Age!