noel and i just chatted about this. one way to make this kind of thing work is to have it as an option in game creation. by default, games would run 24/7, but you could opt to start a "daytime game". when a player tries to join a daytime game, they will get a confirmation dialog that shows them when the game will be active using their local time.
this would hopefully address the danger of a player in an incompatible time zone joins a game that is only active while they are asleep. that player will inevitably do poorly and/or quit, both of which will have a negative impact on the other players' experience (not to mention that they will not be able to communicate effectively with anyone!)
so yeah, this is now on our list. probably a post-release feature, but we like it and plan to add it.