Timezone Converter
Convert time across the world's cities instantly — with live clocks and automatic DST.
Baghdad
12:33:54 AM
Fri, Jul 31
Time zones are not a technical problem but a political one, which is precisely why they are so difficult. There are 38 UTC offsets in current use, some at 30 and 45-minute increments; China spans five geographic zones and uses one; Nepal sits at UTC+5:45 for reasons that are entirely historical; and daylight saving rules change by government decision, sometimes with weeks of notice. This converter handles all of it using your browser's built-in IANA time zone database — the same authoritative dataset that operating systems rely on — so DST transitions and regional oddities are applied correctly rather than approximated.
How the converter works
Pick a source zone and time, then one or more target zones, and the converter shows the equivalent local time in each. Rather than adding and subtracting fixed offsets, it uses the IANA time zone database via the browser's `Intl` API, which knows the actual rules for each region — including when DST starts and ends, which differs by country and changes over time. This is why converting a date in July gives a different offset than the same conversion in January for many zones.
How zones work
UTC is the reference; every zone is an offset from it.
New York = UTC−5 (EST) / UTC−4 (EDT, summer)
London = UTC+0 (GMT) / UTC+1 (BST, summer)
Tokyo = UTC+9 (no DST)
Kathmandu = UTC+5:45 (no DST)
Conversion: local → UTC → target local
DST rules come from the IANA database, not arithmetic.The critical detail is that an offset is not a property of a place — it is a property of a place at a moment. New York is UTC−5 in winter and UTC−4 in summer, so "New York is five hours behind London" is true for part of the year and wrong for the rest. Worse, the transition dates differ: the US changes in March and November, the EU in late March and late October, leaving a two-week window each year where the usual gap is off by an hour. This is why hardcoding offsets always eventually breaks.
What to know about time zones
- 1Never store local times in a database. Store UTC and convert for display. Local times are ambiguous — during the autumn DST rollback, 1:30 AM occurs twice, and during the spring jump forward it does not occur at all. A timestamp stored as local time can be genuinely unrecoverable.
- 2The DST gap weeks catch everyone. The US and EU change clocks on different dates, so for about two weeks in March and one in October, the usual difference between New York and London is off by an hour. Meetings scheduled during these windows go wrong constantly, and calendar apps do not always warn you.
- 3The southern hemisphere runs DST in reverse. When Europe springs forward, Australia falls back. The gap between London and Sydney swings between 8, 9, 10, and 11 hours across the year — one of the widest variations anywhere, and a recurring source of missed calls.
- 4Abbreviations are ambiguous and should be avoided. IST means Indian, Irish, or Israel Standard Time depending on context. CST is Central Standard Time in the US, China Standard Time, or Cuba Standard Time. Use IANA identifiers like `America/Chicago` in anything technical — they are unambiguous and versioned.
- 5Time zone rules change with real political frequency. Countries adopt, abandon, and shift DST regularly, and the IANA database is updated several times a year in response. Systems that ship a bundled copy of the database and never update it will silently produce wrong times after any rule change.
Frequently asked questions
Why do some time zones have 30 or 45-minute offsets?
Because zones are political decisions, not geometric ones. India chose UTC+5:30 as a compromise across a wide country wanting a single national time. Nepal chose UTC+5:45 partly to be distinct from India. Australia's Northern Territory sits at UTC+9:30, and the Chatham Islands use UTC+12:45. Each has its own historical reasoning, and none follows from the geography alone.
How does daylight saving affect conversions?
It changes the offset for part of the year, which means the difference between two cities is not constant. This converter applies the correct rule for the specific date you enter using the IANA database, so a July conversion and a January conversion between the same cities can legitimately differ by an hour. Any tool that treats offsets as fixed will be wrong for months at a time.
What is UTC and how is it different from GMT?
UTC is the modern atomic-clock-based standard and the reference all zones are defined against. GMT is a time zone, historically based on the sun at Greenwich, and today used by the UK in winter. They are within a second of each other and used interchangeably in casual speech, but technically UTC is a standard while GMT is a zone that happens to sit at UTC+0 for part of the year.
Why does China have only one time zone?
A political decision made in 1949 to unify the country under Beijing time. China geographically spans about five zones, so in the far west, the sun can rise around 10 AM by the clock. Xinjiang unofficially runs on a local time two hours behind, meaning some businesses there keep two schedules — an illustration of how time zones follow politics rather than the sun.
How should I schedule a meeting across time zones?
Specify the zone explicitly and prefer a shared reference like UTC for anything written down. "3 PM" is meaningless in a distributed team; "3 PM UTC" is not. Watch for the DST gap weeks, and remember that a meeting recurring weekly will shift for some participants when their zone changes clocks but another's does not — this is why a standing call can suddenly land at 6 AM for someone.