SQL Server has `datetimeoffset` which stores the UTC offset (and so roundtrips it), which is definitely an improvement. (You still may need/want a string timezone column even with UTC offsets, but you don't need a denormalized _utc column because datetimeoffset math just works as if the times were all UTC.) It seems like something that Postgres could use. Especially because the overhead for storing UTC offsets isn't that much. (10 bytes versus 8.)