I've been reworking postgresql-simple's out-of-box support for time types, and as I've come to a better understanding of the issues involved, I've come to realize that I've made a small blunder. Namely, PostgreSQL's "timestamp without time zone" should not be automatically convertible to Data.Time.UTCTime. The "timestamp with time zone" type represents a clear, unambiguous point in time. It corresponds quite nicely to Data.Time.ZonedTime and Data.Time.UTCTime. By contrast, timestamp without time zone can only be understood in some larger context, specific to the application and perhaps even the particular instance of the application. And even with that context, it may turn out to be difficult (or impossible) to decide what point in time such a timestamp actually represents. This corresponds quite nicely to Data.Time.LocalTime. So, in essence, this conversion assumes that LocalTime are always UTCTime, and promoting an ambiguous time to an unambiguous type by assuming one particular time zone. So, do I plan on removing this conversion from postgresql-simple sometime in the near future. I do know that this impacts persistent-postgreql and may well impact others, but I think it's something that needs to be done. I do see that persistent-postgresql does have an upper bound set, so I will increment postgresql-simple's version to 0.2 when this functionality is removed. Part of the rework involves writing my own parsers and printers. These should prove to be significantly faster than those provided by Data.Time, but I don't have numbers yet. (and indeed, the printers aren't yet done.) Also, it introduces types to handle 'infinity' and '-infinity' timestamps and dates. And in the process of "reverse engineering" PostgreSQL's time format, I ended up doing a binary search by hand and discovered the date 1883-Nov-18, which has a particular significance to time geeks. So I've definitely learned some things in this process. Anyone who is interested in reviewing the work I've done so far should check out my "time" branch on github. I would appreciate feedback. https://github.com/lpsmith/postgresql-simple/tree/time Best, Leon