Using periods
A Period adds time-related information to an individual event.
For example, a free loan may be offered to subscribers on each anniversary. This loan is valid for a period of two weeks after the anniversary date.
A period type is used to specify an event concept.
For example, a free anniversary loan is offered every year.

The relationship between a Period type and an Individual event is described by an Event type periodization.
The relationship between a Period and an Event concept is described by an Event periodization.