Only those that have created their own custom datetime library integrations need to do any kind of work migration work.

Custom DateTime Integration Changes

Prior to 0.4.1, the set method in the IsDateTime typeclass had a Option[DateTime] return type. Implementors should return a Some(...) if assigning the new value to the given field succeeded and a None otherwise. This covered two possible cases: 1) Unsupported fields by the DateTime representation and 2) Assigning an invalid value to given field.

In 0.4.1 the signature has changed to return a Either[DateTimeError, DateTime]. Implementors must now return a Right(...) when assigning the new value succeeds and in case of failures they must choose one of the following:

• cron4s.datetime.UnsupportedField: For signalling the fact that the given field is not supported by the DateTime representation.

• cron4s.datetime.InvalidFieldValue: For signalling the fact that the field is supported but given value can not be assigned to the given field.

Please, review the documentation at Custom DateTimes.