World Clock & Time Zone Converter
Enter one date and time for a base city, and instantly see the local time, time difference, and whether it falls within business hours for several comparison cities at once. Daylight saving time is resolved correctly for each date using your browser's built-in time zone database — no stale fixed-offset table. Everything runs in your browser; the date and time you enter are never sent anywhere.
The date and time you enter are processed entirely in your browser and never sent anywhere.
Enter the base date/time and comparison cities, then press "Convert".
How to use
- Enter the base city and the date/time you want to convert from. "Use current time" fills in the current moment automatically.
- Pick one or more cities to compare against. Use "Add a city" to compare several at once.
- Press "Convert" to see each city's local time, the time difference, and whether it falls within typical business hours.
How it works
How the time difference is calculated
This tool does not keep a fixed lookup table of time differences between cities. For the exact date and time you enter, it uses your browser's built-in Intl.DateTimeFormat (which includes the IANA time zone database) to compute the actual UTC offset at that moment.
Many cities switch to daylight saving time (DST) twice a year, shifting their UTC offset by one hour. The exact switch dates differ by country and can even change when a country updates its DST law (the US uses the second Sunday of March through the first Sunday of November; Europe uses the last Sunday of March through the last Sunday of October). A fixed offset table would be wrong for part of the year in any city that observes DST — deferring to the browser's time zone database avoids that class of error entirely.
About the business-hours indicator
The tool marks whether the converted local time falls between 9:00 and 18:00 as a general business-hours guideline. It does not account for local weekends or public holidays — for that, see our business-day calculator tool.
Supported cities
This tool offers a curated list of major cities rather than free-text city entry, so there's no risk of a misspelled or ambiguous city name producing the wrong result.
FAQ
Is the date/time I enter sent anywhere?
No. All calculations happen entirely inside your browser; nothing is transmitted externally.
Does this handle daylight saving time correctly?
Yes. Instead of a fixed offset table, it uses your browser's built-in time zone database to compute the actual offset for the exact date you enter, so it automatically accounts for whether daylight saving time is in effect.
Can I look up a city that isn't in the list?
Not directly in this version — pick the closest city that shares the same time zone as the one you're after.
What does the business-hours indicator mean?
It's a simple guideline showing whether the converted local time falls between 9:00 and 18:00. It doesn't account for local weekends or public holidays, so double-check the local calendar before scheduling a meeting.
How many comparison cities can I add?
You can compare up to 5 cities at once.
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