Protect the occupied time.

Choose the interval between offered starts separately from the length of the appointment and its occupied time.

Minimum lead time should reflect preparation and staffing needs, not just a preference for a fuller calendar.

Open appointments only as far ahead as staffing, location and resource availability can be maintained with confidence.

Confirm which timezone the customer sees and which timezone staff use before relying on matching clock times.

Represent a temporary absence as an exception, then inspect existing commitments separately from newly offered availability.

Treat an extended or shortened day as a dated exception and test which rule wins when settings overlap.

A connected calendar is not proof that every conflict, cancellation or delayed update is handled as you expect.

Validate every occurrence of a recurring series; one available first appointment does not establish the rest.

Check both sides of a move: the new appointment must fit, and the old capacity must be released only under the intended rule.