Calendar displays appointment times in customer's local timezone

Displaying all appointment times in a single server timezone (typically UTC or the business owner's zone) forces customers to do mental arithmetic and guarantees no-shows. A customer in EST booking a slot labeled '14:00 UTC' will arrive at 2 PM local time, six hours late. This directly destroys revenue per missed appointment, generates support tickets, and violates baseline WCAG 3.1.4 abbreviation expectations when timezone labels are absent. High-volume booking platforms lose thousands of dollars weekly to this single defect.

Detect the viewer's timezone with Intl.DateTimeFormat().resolvedOptions().timeZone, then convert every stored UTC timestamp through date-fns-tz before render, and always display the zone abbreviation alongside the time. Update every appointment display component (calendar, confirmation page, email template). See src/components/AppointmentDisplay.tsx:

const userTz = Intl.DateTimeFormat().resolvedOptions().timeZone
const zoned = toZonedTime(appointment.start_time, userTz)
format(zoned, 'MMM d h:mm a zzz', { timeZone: userTz })