Time Zone Converter
Compare a moment across several zones and find the hours that work for everybody.
The Fortnight When Everything Goes Wrong
Time zone arithmetic is easy until it is not. The difficulty is not the offsets — it is that they change, on different dates in different countries. For two weeks each spring and autumn, London and New York are four hours apart instead of five because one has changed clocks and the other has not, and every meeting booked "same time as usual" lands an hour out.
Every conversion here goes through the IANA time zone database your browser already carries, so the offset applied is the one that actually held on that date in that place, daylight saving and historical changes included. Set the date to the week of a clock change and you will see the difference shift.
Key features
- Several zones at once — up to eight, compared against one source time.
- Real daylight saving — the rules for that specific date, not an offset assumed to hold all year.
- Day shifts marked — when a time lands on the next day or the day before, it says so.
- A working-hours strip — every zone's day side by side, with office hours shaded so the overlap is visible.
- Your zone detected — and the full IANA list available, not just the popular ones.
This tool runs entirely inside your browser using native Web APIs. Your files and text are never uploaded to a server, never logged and never shared with third parties.
How to use: Time Zone Converter
- Set the source zone and time
Yours is detected; "right now" fills in the current moment. - Add the zones you care about
Colleagues, clients, family — up to eight. - Read the conversions
Each shows the local time, the offset and whether the date has shifted. - Find the overlap
The shaded band in the strip is where working hours coincide.
Technical specifications
| Processing location | Entirely in your browser — no server round trip |
|---|---|
| Data uploaded | None. Files and text never leave your device |
| Price | Free — no account, no trial, no usage cap |
| Category | Converters |
| Works offline | Yes, once the page has loaded |
| Browser support | Chrome 90+, Edge 90+, Firefox 90+, Safari 15+ |
| Interface languages | English, 中文, हिन्दी, Español, العربية |
Frequently asked questions
Why is the difference from New York sometimes 4 hours and sometimes 5?
Because the UK and the US change clocks on different dates. The US moves in mid-March and early November; Europe moves in late March and late October. For a couple of weeks either side, the usual five-hour gap is four. It is the single most common cause of a mis-booked transatlantic meeting.
Should I use EST or America/New_York?
America/New_York, always. EST means a fixed offset of UTC-5 with no daylight saving, so it is wrong for eight months of the year. The named zone carries the full rules including every change. The same applies to PST, CST and the rest — they are abbreviations for one half of the year.
Does this handle countries with no daylight saving?
Yes. India, most of Africa, China, Japan, Arizona and Queensland all stay put, so their difference from a zone that does change shifts twice a year. The database knows, which is why the tool asks for a date rather than just a time.
Why does the strip shade 9 to 5?
Because it is a widely understood default, not because it is right everywhere. Spain and much of Latin America run later; parts of northern Europe start earlier. Read the shaded band as a starting point and adjust for what you know about the people involved.
What about half-hour and 45-minute zones?
Handled correctly. India is UTC+5:30, Nepal is UTC+5:45, parts of Australia are on 30-minute offsets and Newfoundland is UTC-3:30. The offsets are read from the database rather than assumed to be whole hours.