Meeting Time Across Zones

Features

• ⚠️ Every city shows its local weekday and day shift, because the day shift is what goes wrong
• A 24-hour sweep, one row per hour in the base zone
• Finds the base hours where every city is inside 09:00–18:00, and says so plainly when there are none
• ⚠️ Offsets are read on the meeting date, so the changeover weeks have the right hour differences
• ⚠️ A base-zone time inside the skipped hour of a spring changeover is reported as non-existent, not nudged to a nearby time
• Autumn changeovers — where a clock time happens twice — are flagged, and the earlier occurrence is used
• Any IANA zone; commas, semicolons, newlines and full-width commas all separate the list
• Up to 8 cities compared (beyond that a row stops being readable)
• ⚠️ The result states that 09:00–18:00 is a convention here, not a rule
• Runs entirely in your browser

How to use

1. Enter a candidate clock time in the base zone
2. Choose the date and the base zone, then list the cities to compare
3. Check “that moment” for a day shift, then use the 24-hour sweep to pick a better slot

FAQ

Why show the weekday for every city? Is the time not enough?

It is not, and this is the most common mistake in cross-zone scheduling. Monday 9 am in Shanghai is Sunday 9 pm in New York — a note reading “Monday 21:00” will be understood by your New York colleagues as Monday evening, and they will be a full day late. The day shift is nearly guaranteed between zones more than 8 hours apart, and it is completely invisible in a clock time. So the weekday and the ±1 shift are shown together.

Does daylight saving affect the result?

Yes, and this is where the tool beats remembering a few fixed offsets. Regions do not change their clocks on the same date: Europe changes on the last Sunday of March, the United States on the second Sunday of March, and in the weeks between them the hour difference is not the usual one (New York and London are normally 5 hours apart and 4 hours apart between those dates). Schedule with fixed offsets and a few weeks a year will carry the wrong time, with the recipient simply concluding you miscalculated. Offsets here come from the actual date of the meeting.

Why would a clock time not exist?

On the day daylight saving begins, a stretch is skipped: the clock goes from 01:59 straight to 02:00 (in Europe, 01:00 GMT jumps to 02:00 BST). If you enter a base time inside that skipped window, it simply does not exist in that zone. It is not nudged to a nearby time here — that would produce a real time that is not the one you wrote, and it would look entirely normal.

Why only 8 cities?

Because each row lists every city side by side. Past eight, the row needs horizontal scrolling to read, and then “see at a glance which slot works” stops being true. Better to look at it in two passes than to be handed a table that cannot be read.

Why is “working hours” defined as 09:00–18:00?

It is only a convention this tool uses for the ✓ marks, not a rule. Actual working patterns vary widely (the midday break in southern Europe, late finishes in East Asia, people working remotely), and what really matters is the specific people, not the zones they sit in. So the tool computes the overlap, but whether to use it is your call.