what’s the best way to schedule an activity for example change status of an item everyday from 18 to 19? Do we need to create 2 rules one for start and one for stop?
“Best” in this case is a combination of personal opinion and some of the finer details of what you are actually changing, when, and how. Certainly two rules is the most straightforward. The only downsides to using two rules would be tracking both rules in the case of wanting to make changes to the system (or for some users the proliferation of rules when they simply prefer to keep the list shorter). If you’re worried about extra rules having an impact on the performance of the system, that’s not an issue. A rule sitting idle has almost no footprint.
Using one single rule would require more coding because the rule logic itself would have to identify the difference between the start and stop condition, but this is not too complicated (again depending on the specifics of the situation).
Really, “best” comes down to what you’re comfortable with and can most easily manage/maintain.
Maybe have a look into iCalendar binding