Is daylight saving time (DST) handled correctly?

Yes. The tool uses JavaScript’s `Intl.DateTimeFormat` with the `timeZone` parameter, which looks up rules in the built-in IANA/tzdata database. That database contains current DST rules, historical changes and scheduled future transitions. When the EU switches from summer to winter time on the last Sunday of October at 03:00 (European time), it is handled automatically. Countries without DST such as Japan, China, India, Russia, Iceland and most tropical countries stay on a constant offset. On the world clock, Oslo, London, New York and Sydney shift automatically, while Reykjavik/UTC, Mumbai and Dubai keep the same offset year-round.

What do "next day" and "previous day" mean?

It is the same moment in time, but the target zone’s local date is one day ahead or behind the source local date. Example: 23:00 Monday in Oslo is 07:00 Tuesday in Tokyo (tagged "next day"). 08:00 Monday in Tokyo is 00:00 Monday in Oslo, same day in Oslo. 02:00 Monday in Oslo is 17:00 Sunday in Los Angeles (tagged "previous day"). Useful to avoid booking meetings after midnight without noticing.

Can I add more cities?

The tool ships with a fixed selection of thirteen cities covering all major business zones: Honolulu, Los Angeles, New York, São Paulo, UTC/London, Oslo, Moscow, Dubai, Mumbai, Shanghai, Tokyo, Sydney. The list is fixed so it stays readable and fits on screen. For a custom list you can use `Intl.DateTimeFormat` with an IANA zone ID directly in JavaScript: `new Intl.DateTimeFormat("en-GB", {timeZone: "America/Toronto", hour: "2-digit", minute: "2-digit"}).format(new Date())`. The full list of zones is at iana.org/time-zones.

What about countries that have discussed dropping DST?

The EU voted in 2019 to drop DST, but implementation has been postponed repeatedly and requires coordination between member states. Until an official tzdata update is issued, Oslo, Berlin, Paris and others keep observing regular DST switches. The US (except Arizona and Hawaii) has also debated the Sunshine Protection Act without a law change taking effect. The tool always reflects the current tzdata in your browser, so as soon as your OS updates its zone data you see the new rules automatically.

Time Zone Converter - Compare Times Across Cities

About time zone conversion

The tool interprets the time you enter as local time in the source zone, and shows the same moment in other cities. Daylight saving time (DST) is handled automatically via the browser’s built-in time zone data.

About this tool

Time zone converter shows what time it is in major cities worldwide for a given moment in a chosen source zone. The tool handles daylight saving time (DST) automatically via the browser’s built-in IANA time zone database, and marks whether the target zone falls on the previous or next day relative to the source instant. You get UTC offset (like GMT+02:00 or GMT+05:30) and weekday alongside the local time. Cities cover the Americas, Europe, Middle East, Asia and Oceania across all major business and meeting zones.

How to use it

Pick the source zone from the dropdown. The tool tries to default to your own zone.
Set date and time, or press "Set to now" for the current moment.
Watch the world clock update all cities at once with local time, offset and weekday.
Rows tagged "next day" or "previous day" show the target city has rolled to a different date.

Examples

Standup at 09:00 Oslo

InputEurope/Oslo, 09:00

OutputLondon 08:00, New York 03:00 (same day), Los Angeles 00:00 (same day), Tokyo 17:00, Sydney 18:00

On summer time Norway is UTC+2. A 09:00 standup then hits midnight for Los Angeles colleagues, likely not workable.

Deploy window 22:00 UTC

InputUTC, 22:00

OutputOslo 00:00 (next day), New York 18:00, Tokyo 07:00 (next day), Sydney 08:00 (next day)

For global teams UTC is often the reference. Watch the "next day" tag when planning on-call rotations.

Meeting 14:00 Mumbai

InputAsia/Kolkata, 14:00

OutputOslo 10:30 (summer) or 09:30 (winter), London 09:30/08:30, New York 04:30/03:30

Mumbai is UTC+5:30 year-round (India has no DST). Half-hour offsets are typical for India, Iran, Newfoundland and parts of Australia.

Common use cases

Planning global video meetings and standups across offices in Europe, the Americas and Asia.
On-call rota where you need to know who is awake when an incident fires.
Booking deploy and maintenance windows outside business hours in every region.
Travel and flight planning where landing local time must match departure zone.
Cross-continent support when you want to see when the customer’s office hours fall in yours.

Frequently asked questions

Is daylight saving time (DST) handled correctly?: Yes. The tool uses JavaScript’s `Intl.DateTimeFormat` with the `timeZone` parameter, which looks up rules in the built-in IANA/tzdata database. That database contains current DST rules, historical changes and scheduled future transitions. When the EU switches from summer to winter time on the last Sunday of October at 03:00 (European time), it is handled automatically. Countries without DST such as Japan, China, India, Russia, Iceland and most tropical countries stay on a constant offset. On the world clock, Oslo, London, New York and Sydney shift automatically, while Reykjavik/UTC, Mumbai and Dubai keep the same offset year-round.
What do "next day" and "previous day" mean?: It is the same moment in time, but the target zone’s local date is one day ahead or behind the source local date. Example: 23:00 Monday in Oslo is 07:00 Tuesday in Tokyo (tagged "next day"). 08:00 Monday in Tokyo is 00:00 Monday in Oslo, same day in Oslo. 02:00 Monday in Oslo is 17:00 Sunday in Los Angeles (tagged "previous day"). Useful to avoid booking meetings after midnight without noticing.
Can I add more cities?: The tool ships with a fixed selection of thirteen cities covering all major business zones: Honolulu, Los Angeles, New York, São Paulo, UTC/London, Oslo, Moscow, Dubai, Mumbai, Shanghai, Tokyo, Sydney. The list is fixed so it stays readable and fits on screen. For a custom list you can use `Intl.DateTimeFormat` with an IANA zone ID directly in JavaScript: `new Intl.DateTimeFormat("en-GB", {timeZone: "America/Toronto", hour: "2-digit", minute: "2-digit"}).format(new Date())`. The full list of zones is at iana.org/time-zones.
What about countries that have discussed dropping DST?: The EU voted in 2019 to drop DST, but implementation has been postponed repeatedly and requires coordination between member states. Until an official tzdata update is issued, Oslo, Berlin, Paris and others keep observing regular DST switches. The US (except Arizona and Hawaii) has also debated the Sunshine Protection Act without a law change taking effect. The tool always reflects the current tzdata in your browser, so as soon as your OS updates its zone data you see the new rules automatically.

Technical background

Source-zone time is interpreted as "wall time" and converted to UTC via tzdata: for each guessed UTC instant the zone offset is fetched with `Intl.DateTimeFormat.formatToParts(..., {timeZoneName: "shortOffset"})`, then the UTC instant is derived by subtracting the offset. The same UTC instant is then formatted into every target zone with `hour: "2-digit"`, `minute: "2-digit"` and `weekday: "short"`. Day difference is computed by comparing the `en-CA` ISO date (yyyy-mm-dd) in source and target zones. The zone list is hardcoded in the script using IANA IDs (e.g. `Europe/Oslo`, `America/Sao_Paulo`) since IANA IDs contain slashes that are unsafe in Astro frontmatter. Local zone detection uses `Intl.DateTimeFormat().resolvedOptions().timeZone`. All computation is client-side with no network calls.

World clock