Here you go:
http://allears.net/btp/downtown.htm
It looks like the hours are constant throughout the year. I had to check first since we have never been in slower seasons, but since it isn't inside any of the parks and has not entrance fee, it attracts a lot of locals so it looks like they don't cut the hours. Of course if anyone knows otherwise, please post.
We seem to go to DTD a lot. Especially when we do DHS - we usually leave when we are hungry for a quick EoS!