You can store times in UTC if you want, but that alone doesn't solve the problem. A UTC timestamp alone is not enough information about an event.

Consider a Doctor's appointment for Dec 20, 2026 2pm in Calgary. Regardless of whether its booked a year ahead (ie before the new time zone rules were decided) or a week ahead (after the rules were decided, and consequently a different UTC time), the expectation is that it will be at at 2pm local time.