One instant can belong to two calendar dates
At 13:00 UTC on Tuesday, 27 October 2026, New York reads Tuesday 09:00. Sydney reads Wednesday 00:00, and Auckland reads Wednesday 02:00. These are three displays of the same instant. Copying the Tuesday date from the organizer’s row into every participant’s note would be wrong.
Write the destination date explicitly
When proposing the meeting, give each city its full local date and time. A phrase such as “Wednesday morning in Sydney” is clearer than a bare “12 AM.” Midnight is especially easy to misread in a 12-hour display, so include the date and use a 24-hour table if that makes the discussion easier.
Check the end as well. A meeting may start late on Tuesday and finish early on Wednesday in one city while staying wholly within Tuesday elsewhere. The duration is one elapsed interval, and the local labels need to show both sides of the boundary.
Availability belongs to local weekdays
A Friday afternoon in Los Angeles can be Saturday morning in Sydney. A Monday–Friday availability setting in Sydney should not treat that Saturday as an ordinary workday merely because the base city still says Friday. The planner checks each interval against the relevant local calendar.
Overnight availability is a separate but related case. If someone offers Friday 22:00–06:00, that single Friday-start interval includes Saturday morning. Disabling Saturday as a new shift start does not remove the tail of the shift already begun on Friday.
Review a weekly anchor in every city
A Tuesday anchor can consistently land on Wednesday elsewhere. A clock change may move the local hour enough to alter that date relationship for meetings close to midnight. Read all twelve recurring rows rather than assuming the first row’s weekday relationship will always hold.
Export an unambiguous event
Resolve any repeated or missing local time, then download the calendar file. Its UTC start and end identify the event independently of the calendar’s display zone. After import, inspect the local date in the application you will use. Keep a printed or image timetable alongside the invitation when participants need an easy cross-city reference.
Sources
Follow the original references for the rules and formats used in this guide.