It's March 2nd, 1943. Your user is in Arizona and using your software to plan a meeting with a customer in California. The user asks you to "schedule a meeting with Acme Corp for 9 AM on the first Friday of next month".
California and Arizona are in different time zones.
Between now and then, California will begin daylight savings time as scheduled on March 8th, but Arizona doesn't do DST so they'll stay behind. However, on April 1st, the governor will sign an emergency order moving Arizona to DST, effective immediately.
By the way, on the day of the meeting, the user will have driven to the Navajo reservation to join some colleagues for the phone call. They /do/ use DST in that part of Arizona. Mostly, some parts don't.
You are to (1) correctly display this meeting in your calendar UI for both participants, (2) send an email to Acme Corp with the meeting details, and (3) notify both users when the meeting is about to begin.
yes I was golfing for worst case scenarios with software that deals with time
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!