A World Clock computes world clock from the inputs you provide. It applies the standard formula to the values you enter and returns the result instantly, without sending any data to a server. Time zone converter for meetings. The tool.
Set a base time in your zone, see it across 5 cities. Uses Intl.DateTimeFormat with IANA zones.
The base datetime is parsed in your local timezone, then re-formatted in each target zone using Intl.DateTimeFormat with the corresponding IANA timezone identifier. The browser handles DST transitions automatically via the underlying ICU data. Source: ECMAScript Internationalization API (Intl).
Side-by-side cities. Plan meetings across time zones.
A world clock shows the current (or a chosen) time across several cities at once, so you can answer one practical question: when it is a given hour in one place, what time is it everywhere else? It is the everyday tool of distributed teams, freelancers with overseas clients, families spread across continents, and anyone watching a live event broadcast from another country.
The hard part is not the arithmetic of adding hours, it is the moving parts: each region sits at a fixed offset from Coordinated Universal Time (UTC), but many regions shift that offset by an hour for part of the year under Daylight Saving Time (DST), and a handful use half-hour or quarter-hour offsets. This tool uses the browser's built-in Intl.DateTimeFormat with IANA timezone identifiers (for example America/New_York, Asia/Kolkata) so every offset and DST rule comes from the same maintained database that powers operating systems worldwide.
Every clock on Earth is expressed as a signed offset from UTC. To convert a moment from one zone to another you do not add the two offsets, you anchor the instant to UTC first, then apply the target offset. The formula is short:
UTC instant = local time - source UTC offset target time = UTC instant + target UTC offset net shift = target offset - source offset
Because both offsets depend on the date, the only reliable way to convert is to evaluate each one for the specific day, which is exactly what the IANA database does behind the widget above.
You are in Mumbai (IST, UTC+5:30) and want to schedule a call for your 6:00 PM with a colleague in New York. What time is it there?
| Zone | UTC offset | Notes |
|---|---|---|
| UTC / GMT | +00:00 | Universal reference; UK in winter |
| EST / EDT (US East) | -05:00 / -04:00 | DST observed; NYC, Toronto |
| PST / PDT (US West) | -08:00 / -07:00 | DST observed; LA, Vancouver |
| IST (India) | +05:30 | No DST; covers 3,000 km E-W |
| JST (Japan) | +09:00 | No DST |
| AEDT / AEST (Sydney) | +11:00 / +10:00 | DST observed in NSW, VIC, ACT, TAS |
| CET / CEST (Europe) | +01:00 / +02:00 | DST observed; Berlin, Paris, Rome |
Offsets without a date are ambiguous for any region that observes DST. The two-value entries above (for example -05:00 / -04:00) show the winter offset first and the summer offset second.
When you record a time across zones, write it in ISO 8601 so there is no US-versus-UK confusion, it sorts correctly as plain text, and it is the JSON and API standard.
2026-05-132026-05-13T14:30:00Z (the trailing Z means UTC)2026-05-13T20:00:00+05:30 (IST)P1Y2M3DT4H5M6S (1 year, 2 months, 3 days, 4 hours, 5 minutes, 6 seconds)2026-W20-3 (ISO week 20, Wednesday)Always store the UTC instant plus the original zone, never a bare local time. That keeps the record correct even if a region later changes its DST rules.
Set the base time to one city's working hours, then read the other cities side by side. A workable window is where every city falls roughly between 08:00 and 18:00. For US West Coast and India there is almost no shared daytime, so one side takes an early or late call.
India spans about 30 degrees of longitude (roughly 3,000 km), straddling two natural time zones. In 1906 the colonial administration chose a single offset midway between UTC+5 and UTC+6, and the half-hour offset has stuck. Nepal goes further with UTC+5:45.
Yes. It uses Intl.DateTimeFormat with IANA timezone identifiers such as America/New_York, so the browser applies the correct DST rules and offset for the chosen date. Pick a date in July versus January and the US and EU offsets shift by an hour automatically.
GMT (Greenwich Mean Time) was based on the sun's position at the Royal Observatory in Greenwich. UTC (Coordinated Universal Time) is defined by atomic clocks and is the modern standard. They differ by less than one second, so for civil use they are interchangeable.
Roughly 40 percent of countries skip DST entirely, including India, China, Japan, the UAE, and most of Africa and Asia. The United States, Canada, the EU, the UK, and most of Australia still shift clocks twice a year, which is why their offset changes seasonally.