I am happy to announce a new version of time-recurrence, a library of functions for generating recurring sequences of dates: http://hackage.haskell.org/package/time-recurrence New in version 0.9.0 is a redesigned top layer API. Previously recurrences were described by combining generating functions to get the desired effect. This was quite functional but had the drawback that a recurrence was difficult to persist outside of the Haskell run-time. As of version 0.9.0 this limitation is no more. Now the actual recurrence rule is defined by combining types into a data structure which can either be persisted (and later read back) or evaluated into a function to generate dates. This also means that the type system now enforces correct rule creation! Additionally some convenience functions are available to construct the recurrence rule in a format familiar to previous users of this library. Here is a familiar example: Generate the 15th and 30th of the month, but only during the work week: > jan2011 = ptime "Sat, 01 Jan 2012 00:00:00 -0400" > jan2012 = ptime "Sun, 01 Jan 2013 00:00:00 -0400" > takeWhile (<= jan2013) $ starting jan2012 $ > recur monthly > >==> enum (Days [15,30]) > >==> filter (WeekDays [Monday .. Friday]) [2011-02-15 04:00:00 UTC ,2011-03-15 04:00:00 UTC, 2011-03-30 04:00:00 UTC ,2011-04-15 04:00:00 UTC ,2011-05-30 04:00:00 UTC ,2011-06-15 04:00:00 UTC, 2011-06-30 04:00:00 UTC ,2011-07-15 04:00:00 UTC ,2011-08-15 04:00:00 UTC, 2011-08-30 04:00:00 UTC ,2011-09-15 04:00:00 UTC, 2011-09-30 04:00:00 UTC ,2011-11-15 04:00:00 UTC, 2011-11-30 04:00:00 UTC ,2011-12-15 04:00:00 UTC, 2011-12-30 04:00:00 UTC ] On the road to version 1.0, I plan to add another type layer which strictly enforces RFC 5545 section 3.3.10. As always I encourage feedback, criticism, suggestions and pull requests. I would especially welcome any type system experts feedback: quite a few GHC extensions needed to be turned on to get this to work. -Chris