did The Eleusian mysteries take place in the Fall?

Many of the artifacts found that relate to the mysteries seem to depict seeds and sowing. From that I would guess Spring.

Two festivals of this kind, Eleusinia were held annually the lesser in spring, when the earliest flowers appeared and the great in the month of September. The one in Sept., was a 9 day festival commencing on the night of the 20th, with a torchlight procession. The festival was brought to a close by games, among which was that of bull baiting. Do know that in the secret rites held only by married women, they sacrificed pigs over a small hole that opened into a cave, probably a offering to Hades to let Persephone come back to the upperworld.