Time Zone Converter

Compare the current time — or any date and time you choose — across up to four cities worldwide. Daylight saving time is handled automatically using the browser's built-in Intl API.

Select cities to compare times.

How It Works

Time is stored internally as a single UTC moment. To display it in a given city's local time, the tool uses the Intl.DateTimeFormat API with the timeZone option set to the city's IANA time zone identifier (for example "America/New_York" or "Asia/Tokyo").

The browser's JavaScript engine contains the full IANA time zone database, so historical and future DST transitions are handled automatically — you do not need to manually add or subtract offsets.

IANA identifiers like "America/New_York" are preferred over abbreviations like "EST" because abbreviations are ambiguous (CST could mean US Central Standard Time or China Standard Time) and do not encode DST rules.

When "Now" is selected, the displayed times update every 30 seconds to stay current. When you set a specific date and time, the display is static.

Frequently Asked Questions

Is DST automatically accounted for?

Yes. The Intl.DateTimeFormat API uses the IANA time zone database which contains all historical and scheduled DST transitions. You simply select the city and the correct UTC offset for that date and time is applied automatically.

What is an IANA time zone identifier?

It is a standardised string like "Europe/London" or "Australia/Sydney" that uniquely identifies a time zone including all its DST rules. They are maintained by the Internet Assigned Numbers Authority and used by all major operating systems.

Can I add more than 4 cities?

The tool supports up to 4 city slots. For comparing more time zones, note that many cities share an IANA zone (e.g. Delhi and Kolkata both use Asia/Kolkata) so check whether an existing slot already covers a city you need.

How accurate are the times?

The times are accurate to the second based on your device's clock, which is typically synchronised to an NTP time server. The Intl API applies the correct UTC offset for the chosen city and date, so conversion accuracy is essentially perfect for modern time zones.