How to Convert Time Between Time Zones
Converting time between cities sounds simple until DST gets involved. A timezone converter that only knows UTC offsets will be wrong for roughly half the year for cities that observe Daylight Saving Time. This converter uses the full IANA Time Zone Database — the same dataset embedded in every major operating system — so it applies the correct offset for the specific date you choose, not just the nominal offset.
To convert a time: select your source city, select your destination city, pick a date, and enter the hour and minute. The result updates instantly. The 24-hour visual timeline below the result shows how all 24 hours in the source city map to the destination city, colour-coded by working hours and sleep hours.
Why Timezone Conversion Is Harder Than It Looks
Most people know that New York is UTC−5 and London is UTC+0 — a five-hour difference. But that's only true in winter. In summer, New York is on EDT (UTC−4) and London is on BST (UTC+1) — a five-hour difference again, but both offsets changed. Now consider Sydney, which is on the opposite hemisphere and switches DST in March and October rather than November and March. The window when you're calculating a time that spans a recent DST switch is where mistakes happen.
The EU has debated abolishing DST since 2019 and may still do so. Several US states have passed legislation to stop changing clocks. Countries like Russia permanently shifted to "summer time" in 2014. All of these rule changes propagate through the IANA database as the authoritative record, which is why using a tool backed by IANA data matters — it reflects actual government decisions, not guesses.
Reading the 24-Hour Visual Timeline
The timeline shows all 24 hours of the day across the two cities simultaneously:
- Each column represents one hour in the source city (left number) and its corresponding hour in the destination city (right number).
- Green columns are standard working hours (9 AM – 6 PM) in the source city.
- Purple columns are sleep hours (10 PM – 6 AM) in the source city.
- The destination hour is colour-coded green if it falls in working hours, purple if it falls in sleep hours — making it easy to find windows where both cities are awake and working.
- The selected hour is highlighted with a blue accent border so you can locate your specific time at a glance.
This is particularly useful for scheduling recurring meetings across time zones: look for a column where both the source and destination numbers are green — that's a slot where both cities are in working hours.
Common Timezone Conversion Reference
Here are some frequently converted pairs and their current offsets (live values reflect DST):
| From → To | Standard diff | DST note |
|---|---|---|
| New York → London | −5h (EST→GMT) | Narrows to −4h in spring when NY switches first |
| New York → Tokyo | −14h (EST→JST) | Japan has no DST — gap narrows to −13h in US summer |
| London → Dubai | +4h (GMT→GST) | UAE has no DST — gap widens by 1h when UK observes BST |
| Sydney → London | −11h (AEST→GMT) | AU summer (Oct–Apr) is EU winter — both offsets change but in opposite seasons |
| Los Angeles → Berlin | +9h (PST→CET) | EU and US DST transitions happen 3 weeks apart, creating a transient +8h window |
| Toronto → Mumbai | +10.5h (EST→IST) | India never changes clocks — gap shifts seasonally with Canadian DST |
Time Zone Abbreviations You'll Encounter
Time zone abbreviations are a source of confusion because some are shared across multiple zones. Here are the most common:
- EST / EDT — Eastern Standard/Daylight Time (UTC−5 / UTC−4). US East Coast.
- CST / CDT — Central Standard/Daylight Time (UTC−6 / UTC−5). US Midwest.
- MST / MDT — Mountain Standard/Daylight Time (UTC−7 / UTC−6). US Mountain.
- PST / PDT — Pacific Standard/Daylight Time (UTC−8 / UTC−7). US West Coast.
- GMT / BST — Greenwich Mean Time (UTC+0) / British Summer Time (UTC+1). UK.
- CET / CEST — Central European Time (UTC+1) / Summer Time (UTC+2). Most of continental Europe.
- IST — India Standard Time (UTC+5:30). India does not observe DST.
- CST (China) — China Standard Time (UTC+8). China does not observe DST — the same abbreviation as US Central time but completely different.
- JST — Japan Standard Time (UTC+9). Japan does not observe DST.
- AEST / AEDT — Australian Eastern Standard/Daylight Time (UTC+10 / UTC+11). Eastern Australia.
Scheduling Across Time Zones — Practical Tips
When coordinating meetings across time zones, these habits prevent scheduling errors:
- State the time in UTC when communicating across many zones — "14:00 UTC" is unambiguous. "2 PM EST" is ambiguous if the recipient isn't sure whether you're on EST or EDT.
- Check for DST transitions in the week of the meeting — if any participant's city is about to switch clocks, your standing meeting time will shift by an hour.
- Use the timeline — the 24h visual above makes it easy to find a window where both cities are in working hours (both green).
- Confirm the date format — "03/04" means March 4th in the US but April 3rd in most of Europe. Always write the month in letters (e.g., "Mar 4") when cross-communicating.
Other Time Zone Tools
Need more? These free tools are also available:
- World Clock — live time in 50+ cities, updates every second, add your own cities.
- Meeting Planner — find the best overlap time for up to 5 cities simultaneously.
- Date Calculator — add/subtract days from a date, or calculate the difference between two dates.
Frequently Asked Questions
How does the timezone converter handle Daylight Saving Time?
The converter uses the IANA Time Zone Database, which contains the full DST transition rules for every supported city. When you select a date, the converter automatically applies the correct UTC offset for that specific date — including whether DST was in effect. If you convert a time in March for New York, it correctly uses EDT vs EST depending on whether the date falls before or after the spring transition.
Can I convert a future date and time?
Yes. Use the date picker to select any date — past, present, or future. The converter will apply the correct timezone offset and DST rules for that date. This is useful for scheduling meetings in advance and confirming the local time in each participant's city.
What does the 24-hour visual timeline show?
The timeline shows all 24 hours of the day side by side — for each hour in the source city, it shows the corresponding local hour in the destination city. Green slots indicate standard working hours (9 AM to 6 PM). Purple slots indicate sleep hours (10 PM to 6 AM). The currently selected hour is highlighted. This lets you find overlap in working hours at a glance.
Why might my converted time be off by an hour?
The most common reason is a recent DST transition that your mental model hasn't updated for. For example, if the US has already "sprung forward" but the EU hasn't yet (the two transitions happen weeks apart), clocks that were 6 hours apart are temporarily only 5 hours apart. The converter handles this automatically — trust the result, not your mental calculation.
What is the difference between UTC offset and a named time zone?
A UTC offset like +05:30 is a fixed numerical shift from Coordinated Universal Time. A named time zone like "Asia/Kolkata" is a region whose offset may change with DST rules (though India does not observe DST, so its offset is permanently +05:30). When you see "IST" on the converter, that abbreviation corresponds to a named zone, not just a fixed offset.
Does the timezone converter work offline?
Yes. Once the page loads, all timezone conversion logic runs in your browser using the built-in Intl API and IANA data bundled with your browser. No internet connection is needed after the initial page load.