Resolve conflicting timezones somehow

Depends on #29

From 2018g on, there are several regions where timezones conflict with each other. In #29, I took the approach of simply picking one (by hand). This imposes my own biases and opinions on a complicated situation, though, and is probably not a great way to go.

We should figure out a better model for how to handle this. This almost certainly involves changing the interface to the library.