Spec weekly meeting reminders that survive DST changes

Your calendar app, written in Python, lets people create weekly meetings such as "every Monday at 9:00 in my timezone". It sends a reminder 10 minutes before each one. Today it stores each meeting as a UTC time and adds 7 days to get the next.

Every March and November, support gets tickets about reminders an hour off. An agent will rebuild how meetings are stored and how each occurrence is worked out.

Write the spec you would hand the agent.

What you know:

• Python 3.12 with zoneinfo, Postgres, and a job that sends reminders from a reminders table
• people pick any time of day and live in many timezones
• meetings repeat for years
• the attendees of one meeting can be in different timezones

Then, in a few sentences: what does a vague "compute the UTC time of each occurrence" prompt get wrong?