are stored as "timestamp without time zone," but we are hoping to move toward a timezone-aware model at some point down the road (although not immediately--it might end up being a couple years).
just a quick note that local-time timestamps are also not aware of timezones either, and that is fine that way. only the conversion functions are aware of timezones, e.g. when printing a timestamp into a calendar system defined string of characters that humans can understand, or when e.g. creating a timestamp from user input.
also note that local-time has quite some TODO's documented in its TODO file. but other than that it works.
https://github.com/dlowe-net/local-time/blob/master/TODO.org