I'm on 6.10.1, using the libs provided with the binary of GHC for Mac OS X. I was fooling around with the time package in GHCi and something seems to be off. I have included a transcript. If I take a time diff, then the seconds are positive when the picos are negative and vice versa. -- _jsn |...transcript...| Prelude System.Time> :m + System.Time Prelude System.Time> t0 <- System.Time.getClockTime Prelude System.Time> t1 <- System.Time.getClockTime Prelude System.Time> diffClockTimes t0 t1 TimeDiff { tdYear = 0 , tdMonth = 0 , tdDay = 0 , tdHour = 0 , tdMin = 0 , tdSec = -7 , tdPicosec = 238846000000 } Prelude System.Time> diffClockTimes t1 t0 TimeDiff { tdYear = 0 , tdMonth = 0 , tdDay = 0 , tdHour = 0 , tdMin = 0 , tdSec = 7 , tdPicosec = -238846000000 }