abs +time

data AbsoluteTime
time Data.Time.Clock.TAI
AbsoluteTime is TAI, time as measured by a clock.
addAbsoluteTime :: DiffTime -> AbsoluteTime -> AbsoluteTime
time Data.Time.Clock.TAI
addAbsoluteTime a b = a + b
diffAbsoluteTime :: AbsoluteTime -> AbsoluteTime -> DiffTime
time Data.Time.Clock.TAI
diffAbsoluteTime a b = a - b