[Haskell-cafe] Adding to / subtracting from a LocalTime?

Hi. How do you add to or subtract from a LocalTime? I'm trying to subtract a second from a LocalTime value but the only API's I can find act only on the TimeOfDay part. subSec :: LocalTime -> LocalTime subSec (LocalTime d t) = LocalTime d $ timeToTimeOfDay ((timeOfDayToTime t) - (secondsToDiffTime 1)) I'm obviously on the wrong track as this looks way too complex for what it's trying to achieve. Calling with '2012-08-18 00:00:00' gives '2012-08-18 -01:59:59' which isn't very helpful. How do I get to '2012-08-17 23:59:59'? Thanks, Adde