From Carleton Moodle Docs
When offering or booking time slots in Scheduler, a user might end up with scheduling conflicts, that is, with two overlapping appointments at the same date and time; either within the same scheduler activity, or across several scheduler activities on the system.
Scheduler attempts to warn teachers of such scheduling conflicts, but it does not ultimately enforce conflict-free appointments. When a student makes a booking, however, no checks for conflicts are performed.
(The following describes the situation as of Scheduler 3.1, to be released. Previous versions of Scheduler may differ slightly.)
In the teacher screens, Scheduler will generally warn when a new or updated slot would create a conflict for a teacher. It does not check whether students on the slot have scheduling conflicts.
Slots that happen in the past will never be regarded as conflicting. Since these are normally added/moved for documentation purposes only, it is not useful to check for conflicts in this case.
- Adding or editing a single slot
When the edit form for a single slot is saved, Scheduler will check whether the time range of the slot overlaps with any other slots of the same teacher, in any scheduler activity on the system. If a conflict is found, this will result in a warning message. You can override the warning - and save the conflicting slot nevertheless - by ticking the "Ignore scheduling conflicts" box.
- Adding repeated slots
When adding a series of (empty) slots, Scheduler will check while creating the slots whether any of them conflicts with existing slots for the same teacher.
In case a conflict is found, the behavior depends on the setting "Force when overlap" in the Add multiple slots screen. If this is set to "no", then those new slots that would create a conflict will not be created. If the switch is set to "yes", then existing conflicting slots will be deleted before the new slot is being created.
However, Scheduler will never delete a conflicting slot if students are already booked on it, or if the slot is located outside the current scheduler activity.
- Mark as seen now
When a teacher clicks "mark as seen now" on a student, this will always create an appointment with the student at the current time, with no checks for conflicts performed.
Scheduler does not detect any scheduling conflicts in the student screens. That is, nothing prevents a student from scheduling two appointments at the same time, either in the same scheduler or in separate schedulers.
The assumption here is that students will check their calendars for other commitments (whether Scheduler appointments or otherwise, online or offline) before making a booking.