lens-datetime

The lens-datetime library provides a unified lens based accessors to the various types in Data.Time.Clock, Data.Time.Calendar and Data.Time.LocalTime. This library only tries to make some of the common use-cases convenient, it doesn't aim for completeness. If you want completeness and/or efficiency try the thyme package instead (http://hackage.haskell.org/package/thyme). Demonstration of basic uses. You can then do the following: You can manipulate the date-time values with proper roll-over behavior via the FlexibleDateTime mechanism: