Put one moment in up to six time zones at once and see where the working hours actually overlap, drawn as a lane per zone across the day. Each zone follows its own daylight-saving rules for the date you choose, so a meeting planned in March is not quietly wrong in April.
Zones side by side
6
Cities to choose from
22
Default working window
9-17
Requests made
0
Step by step
How to use it
01Set the reference zone and moment
Your own zone and the time you have in mind, or live to track now. Everything else is expressed relative to this one.
02Add the zones you are coordinating with
Up to six. Each converts using its own daylight-saving rules for the date you picked, which is what makes a plan made in one season hold up in another.
03Read the overlap, not the times
One lane per zone across the source day, with working hours marked. The shared-hours count is the answer to the actual question: when can these people all be awake and at work.
04Adjust the working window
Nine to five is a default, not a fact. Widening it to eight to six often turns zero shared hours into two, which is the difference between a call and an email thread.
Worked example
Why the overlap is the answer
Three zones across ten hours of spread. Converting one time tells you very little; seeing the whole day tells you whether a meeting exists at all.
Given
San Francisco
UTC−8
London
UTC+0
Bengaluru
UTC+5:30
One day, three lanes, 09:00-17:00 working hours
SF 09 10 11 … 17
London 17 18 19 … 01
India 22 23 00 … 06
overlap at 09:00 SF = 17:00 London (just)
= 22:30 India (no)
widen to 08:00-18:00 and SF 08:00 becomes
16:00 London and 21:30 India - still no.
this trio has no shared working hour.
SF ↔ London
~1 hour
SF ↔ India
none
All three
none
Ten and a half hours of spread means no single hour exists where all three are at work, and no amount of scheduling cleverness creates one. Seeing that as an empty overlap rather than a converted time changes the decision: you either rotate which zone takes the inconvenient call, split into two meetings, or accept that this team communicates asynchronously.
Before you send the invite
What to know about time zones
Offsets are not fixed, and countries change them
A zone's offset depends on the date because of daylight saving, and the rules themselves are political — governments move DST dates and occasionally abolish it with months of notice. A conversion is only valid for the date you asked about.
The transition weeks are where meetings break
The US and Europe change clocks on different weekends, so for two or three weeks each spring and autumn the gap between New York and London is an hour off its usual value. Recurring calls silently shift for everyone in one of the two zones.
Not every zone is a whole hour
India is UTC+5:30, Nepal is +5:45, and parts of Australia are +9:30. Any mental arithmetic that assumes whole hours is wrong for a substantial share of the world's population — which is most of why half-hour zones cause so many missed calls.
Abbreviations are ambiguous
CST is Central Standard Time in the US, China Standard Time, and Cuba Standard Time. IST covers India, Ireland, and Israel. Write the offset or the city; never put a three-letter abbreviation in an invitation and assume it was understood.
The southern hemisphere runs DST in reverse
Sydney gains an hour when London loses one, so the gap between Europe and Australia swings by two hours across the year, not one. Anyone coordinating across hemispheres has to re-check their standing meeting twice a year.
Everything is computed locally
Conversions use your browser's own timezone database, so there is no request and no lookup. The share link carries the zones and the moment, which is enough for a colleague to see exactly the grid you are looking at.
The judgement call
How do you schedule across zones?
The overlap tells you which of these situations you are in.
Three or more shared working hours
Just meet
Pick a time in the middle of the overlap and leave room for someone's lunch.
One or two shared hours
Protect the slot
It is the only window that exists. Make it a standing time rather than negotiating it every week.
No overlap at all
Rotate the pain
Someone takes an early or late call. Alternate which zone it is rather than always the smallest team.
A recurring meeting across DST
Anchor to one zone
Fix it in the organiser's zone and accept that it moves for everyone else — or re-check it each transition.
Announcing a launch time publicly
Give UTC + a city
Abbreviations are ambiguous. An offset plus a real city removes both the guesswork and the CST problem.
A team spread over 12+ hours
Go asynchronous
There is no fair meeting time. Written updates beat a call nobody can attend awake.
Reference
How the conversion works
Zones offered
22 citiesChosen to cover the working population people actually coordinate with rather than every IANA zone.
Comparison limit
Up to 6 at onceEach converts with its own DST rules for the date you selected, not with a fixed offset.
Working window
09:00–17:00 by defaultAdjustable. Widening it by an hour at each end is often what creates an overlap where there was none.
Half-hour zones
+5:30, +5:45, +9:30India, Nepal, and parts of Australia. Whole-hour mental arithmetic fails for a large share of the world.
DST transitions
Different dates per countryThe US and Europe switch on different weekends, so the gap between them is briefly unusual twice a year.
Data source
The browser's own zone databaseNo request is made, and the rules are the ones your platform ships and updates.
FAQ
Questions, answered plainly
How do I convert a time between zones?
Set your reference zone and the moment, then add the zones you are coordinating with. Each one is converted using its own daylight-saving rules for the date you chose, and the grid shows the whole day rather than a single converted time.
How do I find a meeting time that works for everyone?
Read the overlap rather than the individual times. The lanes show each zone's working hours across the source day, and the shared-hours figure tells you how many hours exist where everyone is at work — including when the answer is none.
Why is the difference between New York and London sometimes four hours instead of five?
Because the two regions change their clocks on different weekends. For a couple of weeks each spring and autumn the usual five-hour gap becomes four, which quietly moves every recurring transatlantic meeting for one side.
Which time zones are not whole hours?
India is UTC+5:30, Nepal UTC+5:45, and parts of Australia UTC+9:30, along with several others. Any conversion done in your head on whole hours will be off by thirty or forty-five minutes for a very large number of people.
Why should I avoid time zone abbreviations?
They are ambiguous. CST is US Central, China Standard, and Cuba Standard time; IST covers India, Ireland, and Israel. An offset and a real city name — 09:00 UTC−8, San Francisco — cannot be misread.
Does this send anything to a server?
No. Conversions use your browser's built-in timezone database, so the tool works offline. The share link carries only the zones and the moment you selected.
Conversions use your browser's own timezone database. No request is made, and share links carry only the zones and the moment.