Time zone converter

How to read the planner

Each row is one time zone. The 24 cells across are the hours of your chosen day, and each cell is coloured by what time it is in that row's zone at that moment:

• Solid — between 9am and 6pm there. An ordinary working hour.
• Faded — 7–9am or 6–9pm. Early or late, but not unreasonable to ask for.
• Empty — the middle of the night. Do not schedule this and expect anyone to be useful.

A column where every row is solid is a meeting that costs nobody anything. When there is no such column — which happens the moment you have someone in California and someone in Singapore — the honest answer is that somebody has to take the amber slot, and the strip at least lets you see who, and offer to rotate it.

Why the gap between two cities is not a fixed number

"New York is five hours behind London" is true for most of the year and wrong for about three weeks of it. Both countries change their clocks, but not on the same dates — the US moves in mid-March and Britain at the end of the month, so for those two weeks the gap is four hours rather than five. There is a matching mismatch in autumn.

The same thing happens in reverse across the equator. Sydney is on daylight saving in January and London is not; in July it is the other way round. The gap between them moves by two hours over the year, and a meeting series set up in one season quietly drifts in the next.

This is why the tool reads the browser's own IANA time zone database instead of storing offsets. Countries change their rules with a few months' notice — several have abolished daylight saving outright in recent years — and a stored table is wrong from that day on with nothing to indicate it.

Use city names, not three-letter codes

Abbreviations are the most common way these things go wrong. EST is Eastern Standard Time, which New York is only on from November to March; for the rest of the year it is EDT and an hour later. Someone who writes "3pm EST" in July has almost certainly meant 3pm in New York, but they have literally said something an hour earlier.

It gets worse: CST means US Central Standard Time, China Standard Time, and Cuba Standard Time, and IST means India, Ireland and Israel. None of those pairs are close to each other.

Naming the city removes the ambiguity completely, which is why the zones here are written as America — New York rather than EST. If you have to write a time in an email, write "3pm New York time" and nobody has to guess which of two hours or three countries you meant.

Questions

How do I find a meeting time that works across time zones?

Add every participant's zone, then read the planner strip: each row is one zone's local hours across your day, and the hours where every row is solid — inside 9am to 6pm there — are the ones that work for everybody. Where no hour is solid for all of them, the faded cells mark the early and late hours that are still civil.

Does it know about daylight saving?

Yes, including on the changeover days themselves, because it asks the browser's IANA database rather than storing offsets. The date field matters for exactly this reason — the same two cities can be four or five hours apart depending on which day you pick.

Why does it say "next day"?

Because 11pm in New York is already the following afternoon in Sydney, and a converter that shows only the clock time and not the date is the reason people join calls on the wrong day. The badge appears whenever the calendar date differs from yours.

Can I add more than three zones?

Yes, as many as you like — press "Add another zone". The planner grows a row for each and the answer at the bottom accounts for all of them.

Why is EST sometimes wrong for New York?

Because New York is only on EST for part of the year — from March to November it is on EDT, an hour ahead. Naming the city rather than the abbreviation avoids the problem entirely, which is why this tool works in zones like America/New_York instead of three-letter codes.

What is UTC, and is it the same as GMT?

UTC is the reference all other zones are offsets from, and it never changes for daylight saving. GMT is a time zone that happens to equal UTC in winter and is used loosely as a synonym; in Britain it becomes BST in summer, which is where the confusion usually starts.

Is my location sent anywhere?

No. The page reads your browser's own time zone setting to fill in the first field. Nothing is uploaded, there is no account, and it never asks for your calendar.

More tools

• Date calculatorDays between two dates with working days counted, adding and subtracting from a date, and a countdown. Month ends clamped, and a weekend you can set to Friday–Saturday.
• Age calculatorExact age in years, months and days — worked out on the calendar rather than by dividing by 365 — with the Hijri date and the next birthday.
• BMI calculatorYour BMI on both the WHO international thresholds and the Asian cut-offs, where the risk starts lower — plus your healthy weight range in kg. Most calculators show only the first.
• Random pickerGiveaway winners, random numbers, a coin or dice — from the browser's cryptographic source, with the modulo bias other pickers carry measured and removed.
• Unit converterMarla, kanal, murabba, gaz and tola alongside the ordinary ones — with both marla conventions, because two are in daily use and they differ by 21%.
• Base64 & URL encoderBoth directions, with correct UTF-8 — a plain btoa throws on Arabic and emoji and quietly returns a different string for an accent. Both fixed here.

All free, all running entirely in your browser. Built by Maxverse Lab, a remote software studio. Every tool.