Switching Deerling/Sawsbuck formes in X&Y?

Question

How does one trigger forme-switches with Deerling / Sawsbuck in X/Y? So far all I've been able to get are Spring Forme Deerling...

Answer 1

A question that touches on this topic has been asked before
http://pokemondb.net/pokebase/169714/im-confused-about-the-seasons-in-x-and-y

Comments

Thanks. It didn't show up when I made a search for similarly-worded questions before creating this one.