OptionalpractitionerOptionalpractitionerBoth sides may enter the waiting room from this instant.
Past this instant the PATIENT may no longer cancel; the clinic still can.
The VIEWER's zone — the timezone (or patientTimezone) the request
carried, else the clinic's. Render startsAt in this one and label it;
an unlabelled appointment time is a support call.
The clinic's zone.
The physician's calendar zone, once a physician is assigned; null before.
When its offset at startsAt differs from timezone's, show the
physician's clock as a second line ("08:00 CEST for Dr Morin") — the
confirmation notices do the same.
The zone the PATIENT booked from (patientTimezone on the booking call,
or the device zone of the booking surface), or null when none was sent —
notices then fall back to the clinic's zone.
A booked appointment, as every surface renders it. The instants are absolute; the four zone fields say whose clock to show them on.