One instant can have several local dates
Use UTC as the shared anchor, then read every local date.
A common reference
The planner inspects candidate starts on one UTC calendar date. A start at 23:30 UTC can already be tomorrow for one person and still today for another. The selected-meeting table therefore prints dates as well as times. Do not copy only the hour into a message.
A worked example
At 14:00 UTC on 11 November 2026, the example places show 14:00 in London, 09:00 in New York and 19:30 in Kolkata, using the rules available to the browser. A 60-minute meeting ends at 20:30 in Kolkata. If that desk's declared window ends at 20:00, the meeting does not fit even though its start does.
Duration matters
Each candidate is tested for its full elapsed duration in one-minute steps, not just its start. Starts are offered every 15 minutes. End boundaries are exclusive: a meeting ending exactly when a window closes fits, while a meeting extending one minute further does not.
The UTC date limits candidate starts, not the local dates people may see. A late candidate may end on the next UTC date. Local weekdays are evaluated throughout the meeting. There is no calendar connection, holiday database or confirmation of a real person's free time.