When you add a schedule in On call schedule, the schedule appears in Time Period. You can then edit date/time information from Time Period.
However, you can not add a new On call schedule from Time Period. And the only place to edit members is from On Call schedule.
We would like the two modules to be more integrated. It would be easier to edit all information from Time Period.
When a user add vacation in their calendar, this is not reflected in the On Call Schedule.