In lack of a better name, common base type for the classes that describes when to run a cron job
A set of different time points, for example "0,15,45"
A range that is scoped by it's position/unit, for minute it would allow "0-59" for example.
Execute something at one single point in time, do not repeat.
All time points in the unit, the "*" in minute position would trigger each minute when the other units are matching
Provides a simplified subset of the time expression part of the V7 cron expression standard.
The simple crontab actor looses its state upon stop, does not remember what jobs has already been run.
Allows for a concise type safe declaration of cron expressions.