The default behavior for Event Timer is to count time sequentially. However in the real world this is not the case, for example, sundays maybe does not count in a due date and hours can be applicable when an office is open. Event Timer can used in combination of Bpm Calendars. The Timer will use the Calendar if particular day or hour should be taken into account when a due date is calculated.
Check calendars at: Calendars in Bpm Flow
In the example above the timer will be activated if the [lastExecutionTime] plus [termValue] is less than current time. In this case [termValue] was defined in a previous step in the process. Also the calculation of days is bound a calendar named [Default]. This calendar for example can have Sundays and Saturdays disbable.
Note: Bpm Flow can have N defined calendars.