The Complete Guide to Timezone Conversion for Developers
Master timezone conversion as a developer. Learn how UTC offsets, IANA timezones, DST, and ISO 8601 work, and avoid common pitfalls.
Jun 17, 2026
World Clock
Display current time across multiple time zones simultaneously. Add any time zone from 80+ cities worldwide.
World Clock
- Select time zones — Choose cities from the dropdown and click "+ Add" to add them to the display.
- View current time — Each card shows the current time, date, and UTC offset for that time zone.
- Toggle format — Switch between 12-hour and 24-hour time format using the toggle button.
- Remove zones — Click the "×" on any clock card to remove it from the display.
- Reset — Click "Reset Defaults" to restore the default set of major world time zones.
Are the times updated in real time?
Yes. The clocks update every second to show the current time for each selected time zone.
Does this account for Daylight Saving Time (DST)?
Yes. The clock uses the browser's built-in time zone database via the Intl.DateTimeFormat API, which automatically handles DST transitions for each time zone.
What time zones are available?
Over 80 time zones covering all major cities across North America, South America, Europe, Asia, Africa, Australia, and the Pacific Islands.
Can I save my custom time zone selection?
Currently, selections are not persisted between page loads. You can add your preferred time zones each session. The default set includes 16 major world time zones.