About Time Zone Conversion
Time zones divide the world into regions that share the same local time. They are defined relative to Coordinated Universal Time (UTC), the global reference clock. A zone's offset from UTC can be a whole number of hours, or a half- or quarter-hour in some regions (India is UTC+5:30, Nepal is UTC+5:45, Chatham Islands are UTC+12:45).
The complication is daylight saving time (DST). Roughly 70 countries shift their clocks forward by an hour during their summer — but not on the same dates, and not always at the same time. The Northern Hemisphere shifts in March and back in November; the Southern Hemisphere does the reverse. A handful of countries switch on different dates each year and others have abolished it entirely.
This tool uses the IANA time zone database (via the browser's Intl.DateTimeFormat API), which contains the authoritative rules for every time zone and their historical DST changes back to the 19th century.
Understanding UTC offsets
| Region | Standard offset | Summer offset (DST) |
|---|---|---|
| London (UK) | UTC+0 (GMT) | UTC+1 (BST, March–October) |
| Paris / Berlin | UTC+1 (CET) | UTC+2 (CEST, March–October) |
| New York (US East) | UTC−5 (EST) | UTC−4 (EDT, March–November) |
| Chicago (US Central) | UTC−6 (CST) | UTC−5 (CDT, March–November) |
| Los Angeles (US West) | UTC−8 (PST) | UTC−7 (PDT, March–November) |
| Dubai (UAE) | UTC+4 (GST) | No DST |
| Mumbai / Delhi | UTC+5:30 (IST) | No DST |
| Tokyo (Japan) | UTC+9 (JST) | No DST |
| Sydney (Australia) | UTC+10 (AEST) | UTC+11 (AEDT, October–April) |
How time zones interact across the globe
The current spread of zones ranges from UTC−12:00 (Baker Island, uninhabited) to UTC+14:00 (Kiritimati, Line Islands). This means there are always between 26 and 27 hours of calendar-date difference happening across the globe at any given moment. When it is Monday in Kiritimati, it is still Sunday in Honolulu.
Common reference times
| Event | UTC time | Impact |
|---|---|---|
| UTC is the reference | 00:00 | All zones computed from here |
| US East Coast business opens | 13:00 | NYC 9 AM start |
| Europe business opens | 08:00 | London 9 AM (BST) |
| India business opens | 03:30 | Mumbai 9 AM |
| Japan business opens | 00:00 | Tokyo 9 AM |
Common use cases
Remote Meetings
Find a time that works across multiple teams in different cities.
Flight Planning
Convert departure and arrival times to your local time zone.
Live Events
Work out when a match, concert or stream starts where you are.
Software Development
Debug server timestamps across different regions.
Client Communication
Check business hours before sending or calling.
Global Teams
Plan stand-ups and syncs across distributed teams.
Privacy and accuracy
This time zone converter runs entirely in your browser. All conversions use the browser's native Intl.DateTimeFormat and Intl.supportedValuesOf APIs, which are backed by the operating system's IANA time zone database. Nothing is uploaded, stored or logged.