Time Zone Meeting Planner

What this planner does

Scheduling across time zones is deceptively hard. A call that feels like a reasonable mid-afternoon to you might be the middle of someone else's night, and once you add a third or fourth location the mental arithmetic falls apart — especially when daylight saving time shifts some zones but not others. This tool removes the guesswork. You add the zones your team works in, pick a date, and a 24-hour grid shows you at a glance which hours are comfortable for everyone.

Each row is one time zone. Each column is one hour of the reference day. Every cell is colored by how that hour feels locally: green for core working hours, amber for the early-morning and evening fringe, and red for night. A good meeting slot is a column that is green — or at worst amber — all the way down. Click any column and the tool spells out the exact local time in every zone, so you can paste it straight into an invite.

Everything is computed in your browser using the standard Intl date APIs. There is no upload, no account and no server — just instant, private scheduling math.

How time zones and DST actually work

A time zone is an offset from Coordinated Universal Time (UTC), the global reference clock. New York in winter is UTC−5; Berlin is UTC+1; Tokyo is UTC+9. To find someone's local time you take the shared UTC instant and add their offset.

The complication is daylight saving time. Many regions shift their clocks forward an hour in spring and back in autumn, so a zone's offset is not fixed — New York is UTC−5 in January but UTC−4 in July. Worse, the change dates differ between countries, and some places do not observe DST at all. That means the gap between two cities can be different depending on the time of year, and there are even brief windows where the usual difference is off by an hour because one side has switched and the other has not.

This planner sidesteps all of that by working from real instants. For each hour of your chosen date it constructs the precise UTC moment — the same kind of absolute instant you can inspect with the Unix Timestamp Converter — and asks the browser to format it in each target zone. Because the browser resolves the offset — DST included — for that exact instant, the grid is correct for the date you picked, not for some generic average. Change the date across a DST boundary and you will see the overlap shift accordingly.

Why overlapping working hours matter

Remote and distributed teams live or die by their overlap window — the stretch of the day when everyone is realistically online at the same time. A team spread across San Francisco, London and Bangalore might share only two or three usable hours. Knowing exactly where that window sits lets you protect it for the things that genuinely need everyone live (decisions, kickoffs, retros) and push everything else to asynchronous updates.

Get it wrong and the cost is real: someone is always dialing in at 6 a.m. or 11 p.m., meetings drift later and later for the team member who keeps "taking one for the group", and resentment builds quietly. Seeing the whole day as a colored grid makes the trade-offs visible and fair — you can immediately tell whether a proposed slot lands in working hours for everyone or quietly dumps the burden on one zone.

How to read the grid

1. Add your zones. Your own zone is detected and added first. Use the search box to add others — type a city like "Tokyo" or "Sao Paulo" and pick it from the list. Each option shows its current offset.
2. Set the reference date. The grid recalculates for that specific day, so daylight saving is handled correctly.
3. Scan for green columns. A column that is green top to bottom is inside working hours for every zone — your best candidate. Amber is workable for an occasional or important call; red means someone would be up at night.
4. Click an hour column. The planner lists the exact local time in each zone for that moment, flagging when a zone has rolled over to the previous or next day.
5. Remove zones you do not need with the small × beside each row to keep the grid focused.

The hour shown in each cell is the local clock in that zone, so you can read someone's day directly: if the cell says 14 it is 2 p.m. there.

Tips for scheduling across zones

• Rotate the pain. If no slot is comfortable for everyone, alternate which zone takes the awkward hour rather than always favoring headquarters.
• Protect the overlap. Reserve your shared green window for synchronous work and move status updates, reviews and docs to asynchronous channels.
• Watch the DST gaps. In spring and autumn, double-check meetings that fall near a clock change — the usual time difference can be off by an hour for a week or two. Picking the actual meeting date in this tool catches that automatically.
• Confirm the date, not just the time. When a zone is many hours ahead, your Tuesday afternoon can be their Wednesday morning. The selected-hour readout flags day rollovers so nobody shows up a day early, and once the slot is locked a countdown to the agreed date keeps everyone aware of how long is left.
• Agree on a reference zone in writing. Always state the zone (or UTC) in the invite. "3 p.m." alone is the single most common cause of missed cross-zone meetings.

Computed locally, kept private

This planner never sends anything anywhere. It relies on the time-zone database and formatting that ships inside every modern browser, so the full list of zones, the offsets and the DST rules are already on your device. All the tool does is ask those built-in APIs to format the same set of instants in each zone and color the result. Your schedule, your team's locations and your meeting plans stay entirely on your own machine — free to use, with no sign-up and no tracking.