Back in gen 5 it was based off of the season, which changed every month. How does it work now?
Starting in Generation VI, with the abandonment of seasons as a mechanic, Deerling and Sawsbuck are no longer able to change their form. All wild and NPC Trainer-owned Deerling and Sawsbuck are in Spring Form, while bred Deerling are in the same form as their mother, or the same form as the Deerling or Sawsbuck parent if bred with Ditto. The Summer, Autumn, and Winter forms are only obtainable via transfer from a Generation V game or from Pokémon GO.
Tldr: Only spring form unless transferred from Gen V or GO.
Source
alright http://www.gamefaqs.com/boards/696959-pokemon-x/67510083 there is no answer but the biggest thought was by your 3ds clock timezone hope it helps :D