Create DSL for building cron expression definitions and defining parsers. Add parser registry. Encapsulat field validations and transformations. Expose parsing result in a generic way to decouple parsing result from interpretation. Add support for optional last field. Definitions for cron4j, quartz and unix crontab parsers.
Deprecate classes. Restructure packages.
Create descriptor object and description strategies, to decouple description from cron expression and bind it to parse result. Use locale instance and avoid invoking static locale method as well as setting static locale variable: locale state is mantained by descriptor object.