Calendar means time and place
Use Calendar for commitments that happen at a specific time or on a specific day. A task that could happen any time usually belongs in Tasks instead.
Add the location and useful link when you have them. That gives you one place to reopen the appointment later.
Search by what you will remember
Appointment titles, locations, notes and other text can be found through Search. You do not need to memorise which week or month something sits in.
Use clear titles such as “Dentist check-up” or “Call with accountant” rather than generic labels such as “Appointment”.
Edit the real record
When a time changes, update the existing event rather than creating a second version. That keeps Today, Calendar and Search pointing to the same record.
Delete an event only when it no longer needs to exist; changing a plan is usually an edit, not a duplicate.