Time Zone Converter and World Clock with Offsets

The World Clock panel of the date tool keeps live cards for saved zones and converts one wall time between them. Each card shows the current local time, the date, a day/night glyph, the zone's UTC offset and its distance from your own zone. Convert a time takes a wall time in one zone, resolves it to a single UTC instant and prints a table: the UTC row first, then every saved zone with its local time and IANA offset — including the half-hour and quarter-hour zones. Offsets come from the browser's IANA database, so daylight saving is applied for the date you enter.

Updated 2026-10-01Reviewed by CalcX Editorial Team4 sources3 min read

How to use it

Read or prune the cards.Every saved zone ticks from the browser clock; the × removes a card and Reset restores the twelve defaults.
Add a zone.Type into the datalist field (for example Asia/Kathmandu) and press Add; the full IANA zone list is offered.
Convert a wall time.Choose a date-time and the zone it is written in; the table lists UTC and every saved zone. UTC is the anchor — read it before the city rows.

Worked examples

Captured with the browser in UTC+8 at a fixed clock of 2026-10-07 12:00.

Convert 2026-01-15 12:00 Asia/Shanghai	Local time	Offset
UTC	2026-01-15 04:00	UTC+0
Tokyo	Thu, Jan 15, 13:00	UTC+9
Kolkata	Thu, Jan 15, 09:30	UTC+5:30
London	Thu, Jan 15, 04:00	UTC+0
New York	Wed, Jan 14, 23:00	UTC−5
Sydney	Thu, Jan 15, 15:00	UTC+11

At the fixed clock the cards read Shanghai 12:00:00, London 05:00:00 (UTC+1, dark, −7h), New York 00:00:00 (UTC−4, −12h) and Sydney 15:00:00 (UTC+11, +3h).

Daylight-saving boundaries need care, and New York shows why:

Convert	UTC row	New York row
2026-03-08 02:30 America/New_York	2026-03-08 06:30	Sun, Mar 8, 01:30, UTC−5
2026-11-01 01:30 America/New_York	2026-11-01 05:30	Sun, Nov 1, 01:30, UTC−4

On 8 March 2026, 02:30 never happens in New York: the spring-forward gap swallows that hour, and the wall time resolves to 01:30, an hour before the time typed. On 1 November 2026, 01:30 happens twice; the converter returns the earlier, daylight-time instance (UTC−4). Both rows look like 01:30, yet the UTC rows are an hour apart — so near a transition, trust the UTC anchor, not the city row.

Limits

Offsets are only as fresh as the browser.: The converter reads the IANA data shipped with the browser or operating system; a very old build can carry outdated transition rules.
Saved zones are local.: The card list lives in this browser's storage; Reset discards it.
What it does not do.: It translates instants, not spans: it will not tell you how many days remain until a date, nor read an epoch number. For calendar spans and workdays use Date Difference; to turn a Unix value into a zoned clock use Timestamp.

Where it helps

Scheduling across regions

Type the hour you mean in your own zone and read the other side's local time from the table instead of doing offset subtraction by hand — Kolkata's UTC+5:30 column makes the arithmetic that would go wrong obvious.

Checking a transition date

Before a recurring meeting crosses a daylight-saving change, convert a sample date on either side. The two New York rows above show why the UTC anchor matters more than the local reading.

References

IANA, Time Zone Database, iana.org （访问日期：2026-10-01）— the offsets and DST transitions behind every row.
Wikipedia, Time zone （访问日期：2026-10-01）— wall time and UTC offset notation.
Wikipedia, Daylight saving time （访问日期：2026-10-01）— the gap and the twice-occurring hour.
ISO, ISO 8601-1:2019, Date and time — Representations for information interchange, iso.org （访问日期：2026-10-01）— UTC and offset representation.