NominalDiffTime is, among others, a Fractional, so you can divide your result with nominalDay:
Prelude Data.Time.Clock> myDiffTime / nominalDay
2.314814814814s
You can use its RealFrac instance to round, floor, etc. it:
Prelude Data.Time.Clock> round $ myDiffTime / nominalDay
2
Prelude Data.Time.Clock> truncate $ myDiffTime / nominalDay
2
Prelude Data.Time.Clock> floor $ myDiffTime / nominalDay
2
Prelude Data.Time.Clock> ceiling $ myDiffTime / nominalDay
3