The ScheduleRule API was designed to disallow sharing of DaySchedules. So if you create the DaySchedule first and pass it in, you will have to delete the original yourself. If you use the other constructor (with a ScheduleRuleset but not ScheduleDay) the ScheduleRule will construct its own ScheduleDay. You can get that from the ScheduleRule ScheduleRuleset later and modify it.