Time Zone Converter & World Clock

about this tool

Where the times come from

Every offset, abbreviation and wall-clock reading here comes from Intl.DateTimeFormat, which carries the IANA time zone database your browser ships. Nothing is fetched and no library is involved, so the answers are as current as the browser's last update, which is how current your operating system's own clock is. Zones are named the IANA way, Area/City; the picker offers every name the browser lists plus a few common aliases (such as Asia/Kolkata, which some browsers list only as Asia/Calcutta), and any name the browser accepts can be typed.

The two daylight-saving traps

Converting an instant into any zone is easy; the hard direction is turning a time someone typed — "09:00 in New York on 8 March" — back into an instant, because on two days a year that time is not what it seems.

On the day the clocks go forward there is a gap: in the United States the clock jumps from 01:59 to 03:00, and 02:30 never happens. The converter moves such a time forward by the size of the gap, as operating systems do, and says so in red rather than silently. On the day the clocks go back an hour repeats: 01:30 happens in daylight time and again in standard time. The converter shows the first occurrence and tells you there were two. Zones with half-hour shifts (Lord Howe Island moves by thirty minutes) are handled the same way, and a test walks every hour of its changeover day.

Reading the converter

Each converted row shows the local time, whether it falls on the same day or the day before or after in that zone, the weekday and date, the abbreviation and offset, the difference from the source in hours and minutes, whether the zone is on daylight time, and a note if that zone changes its clocks on that very day. Leaving the date and time blank converts "now".

The meeting planner

The grid takes each hour of the chosen day in the source zone and shows what every other zone's clock reads at that moment. Cells in working hours (09:00–17:00 local) are shaded; a column where every zone is at work is marked in green and summarised in the heading. Cells whose time falls on the previous or next day carry a −1 or +1.

Limits

Working hours are fixed at 09:00–17:00 and do not know about weekends, holidays or lunch. Abbreviations are the browser's: unambiguous ones such as EST appear, the rest are shown as an offset, because IST means three different things. Historical zone rules follow the browser's database, which is reliable for recent decades and approximate before the 1970s.

A stored timestamp carries no zone at all, which the Unix timestamp converter explains and decodes. For the number of days or hours between two moments, date difference & duration.

questions

Why did 02:30 turn into 03:30?

Because on the day the clocks go forward that time does not exist: in the United States on 8 March 2026 the clock jumps from 01:59 to 03:00. The converter moves the time forward by the size of the gap, which is what every operating system does, and says so.

Why does it say a time happens twice?

On the day the clocks go back, an hour repeats: in New York on 1 November 2026, 01:30 happens once in daylight time and again an hour later in standard time. The converter uses the first and tells you, so you can pick the second if that is the one you meant.

Where are the time zone names from, and why is Kolkata sometimes Calcutta?

They are IANA zone names, the ones every operating system and programming language uses, in the form Area/City. Some cities were renamed and the database keeps the old name as an alias; browsers differ in which they list. Either spelling works here.

Why does it show GMT+5:30 instead of IST?

Abbreviations are ambiguous — IST is India, Ireland and Israel — so the browser only supplies the ones that are unambiguous in English, such as EST, and gives an offset for the rest. The offset is always shown and is the unambiguous form.

Can I change the working hours in the planner?

Not yet; they are 09:00 to 17:00 local time in every zone, which is the usual first approximation. The grid still shows every hour, so a different working day can be read off by eye.