An event is only included in CARDS month-end processing once it has been finalized. The session date is used during the ratings' update (but see below for further details on this point).
When you run the export option at the end of month all the events in the date range selected will be displayed in the list. NOTE this is the event date, not the date of the sessions within the event. The session dates within those events are used during the update process and are used to identify the uniqueness of the sessions of play.
Therefore events with many sessions need to be handled carefully, particularly where it spans the end of month. This can be handled in one of two ways.