Hi Cafe, I have encountered the following puzzling behaviour from a very simple program: Consider -- {-# LANGUAGE RebindableSyntax #-} module A where import Data.Time running this with ghci gives: A> :i UTCTime type UTCTime :: * data UTCTime = UTCTime {utctDay :: Day, utctDayTime :: DiffTime} -- Defined in ‘time-1.9.3:Data.Time.Clock.Internal.UTCTime’ instance [safe] Eq UTCTime -- Defined in ‘time-1.9.3:Data.Time.Clock.Internal.UTCTime’ instance [safe] Ord UTCTime -- Defined in ‘time-1.9.3:Data.Time.Clock.Internal.UTCTime’ instance [safe] Show UTCTime -- Defined in ‘time-1.9.3:Data.Time.LocalTime.Internal.ZonedTime’ instance [safe] FormatTime UTCTime -- Defined in ‘time-1.9.3:Data.Time.Format.Format.Instances’ instance [safe] Read UTCTime -- Defined in ‘time-1.9.3:Data.Time.Format.Parse’ instance [safe] ParseTime UTCTime -- Defined in ‘time-1.9.3:Data.Time.Format.Parse.Instances’ Now uncomment the first line (RebindableSyntax) and rerun it: A> :i UTCTime type UTCTime :: * data UTCTime = UTCTime {utctDay :: Day, utctDayTime :: DiffTime} -- Defined in ‘time-1.9.3:Data.Time.Clock.Internal.UTCTime’ instance [safe] FormatTime UTCTime -- Defined in ‘time-1.9.3:Data.Time.Format.Format.Instances’ instance [safe] ParseTime UTCTime -- Defined in ‘time-1.9.3:Data.Time.Format.Parse.Instances’ And all of the nice instances for UTCTime have disappeared. Why? Best wishes, Henry Laxen