Free World Clock & Time Zone Converter
Look up the current local time in any of 40+ major cities worldwide, compare multiple time zones side-by-side, and see each city's location on an interactive map.
New York
Thu, Jun 11 · UTC+9
London
Thu, Jun 11 · UTC+9
Dubai
Thu, Jun 11 · UTC+9
Tokyo
Fri, Jun 12 · UTC+9
Add / remove cities (4 selected)
Quick answer
World time zones are offset from Coordinated Universal Time (UTC). For example, New York (EST) is UTC−5 in winter and UTC−4 (EDT) in summer; Tokyo is always UTC+9. To convert a time, find the UTC offset of both cities and add or subtract the difference. London is UTC+0 in winter — when it is 12:00 in London it is 17:00 in Dubai (UTC+4) and 21:00 in Tokyo (UTC+9).
Formula & method
Each city's current time is computed in your browser from your device clock using the built-in Intl.DateTimeFormat API with the city's IANA time-zone identifier (for example America/New_York or Asia/Tokyo), so daylight-saving shifts apply automatically. To convert a specific time between zones, both cities are expressed as UTC offsets and the difference is added. Markers sit on a Leaflet/OpenStreetMap map at each city's latitude and longitude. Nothing is fetched from a server.
Examples
- Input
- 10:00 AM EST (UTC−5)
- Result
- Tokyo: 11:00 PM JST (next day) (UTC+9)
- Why
- Tokyo is UTC+9, New York EST is UTC−5. Difference = 9 − (−5) = 14 hours ahead. 10:00 + 14h = 24:00 = midnight, which rolls to 00:00 next day, or 11:00 PM on the same calendar day in Japan (since Japan is 14 hours ahead).
- Input
- 12:00 PM GMT (UTC+0)
- Result
- Dubai: 4:00 PM GST (UTC+4)
- Why
- Dubai (GST) is UTC+4 — exactly 4 hours ahead of UTC. 12:00 + 4h = 16:00 (4:00 PM).
- Input
- 9:00 AM PST (UTC−8)
- Result
- Berlin: 6:00 PM CET (UTC+1)
- Why
- Berlin CET is UTC+1, LA PST is UTC−8. Difference = 1 − (−8) = 9 hours ahead. 09:00 + 9h = 18:00 (6:00 PM).
- Input
- 8:00 AM AEDT (UTC+11)
- Result
- New York: 5:00 PM EST (previous day) (UTC−5)
- Why
- New York EST (UTC−5) is 16 hours behind Sydney AEDT (UTC+11). 08:00 − 16h = −8h = 4:00 PM the previous day. This illustrates how the International Date Line works — Sydney is already a day ahead.
When to use this tool
- Scheduling international calls, meetings, or webinars across multiple time zones.
- Checking whether a business or office is currently open in another country.
- Planning international travel connections or layovers.
- Tracking world markets (stock exchanges open at specific local times).
Common mistakes
- Ignoring daylight saving time (DST) — many countries shift their clocks ±1 hour seasonally, changing UTC offsets.
- Assuming all countries use whole-hour offsets — India (UTC+5:30), Nepal (UTC+5:45), and Iran (UTC+3:30) use half or quarter-hour offsets.
- Forgetting the date can change — converting a morning time in the Americas to Asia often crosses midnight and changes the date.
- Using abbreviations ambiguously — CST means UTC−6 (US Central) in North America but UTC+8 (China Standard) in Asia.
Frequently asked questions
What is UTC and why is it used as a reference?
UTC (Coordinated Universal Time) is the primary time standard used worldwide. It does not observe daylight saving time and is essentially equivalent to GMT. All time zones are expressed as UTC offsets (e.g. UTC+9 for Japan, UTC−5 for US Eastern Standard Time).
What is the difference between GMT and UTC?
They are functionally the same for everyday purposes. UTC is the formal international standard maintained by atomic clocks, while GMT (Greenwich Mean Time) is a time zone based on the meridian through Greenwich, UK. In practice both refer to an offset of 0.
How do daylight saving time changes affect conversions?
When DST is in effect, a country's UTC offset changes by +1 hour. For example, US Eastern Time switches between UTC−5 (EST, standard time) and UTC−4 (EDT, daylight time). Always check current UTC offsets around March and November for countries that observe DST.
Does every country observe daylight saving time?
No. Much of Asia (Japan, China, India), Africa, and parts of South America do not observe DST. EU countries are debating abolishing it. The US and most of Europe still shift clocks in spring and autumn.
What time zone does India use?
India uses IST (Indian Standard Time), which is UTC+5:30 — a half-hour offset. It does not observe DST.
How do I convert between time zones manually?
1) Convert the source time to UTC by applying the source UTC offset (subtract to go forward, add to go back). 2) Apply the destination UTC offset to get local time there. Example: 3:00 PM JST (UTC+9) → UTC = 3:00 − 9h = 06:00 UTC → NYC EST (UTC−5): 06:00 − 5h = 01:00 AM.
Sources & references
External references open in a new tab. We are independent and not affiliated with these organizations.
- ✓ Free to use
- ✓ No sign-up required
- ✓ Runs entirely in your browser — nothing is uploaded.
- ✓ Formula and method shown above
Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.
Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.
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