Convert any time between multiple time zones simultaneously with DST awareness.
This tool converts one moment into as many time zones as you add. Enter a date, a time, and the city it was written in, and it shows the equivalent local time in every other zone on your list. Offsets follow each zone's real daylight saving rules for that exact date rather than a fixed number you remember. The thing people most often get wrong is assuming the gap between two cities is constant: New York and London differ by five hours for most of the year, but for a few weeks around their differently timed spring and autumn transitions the gap is four hours.
A concrete input and expected output from the current implementation.
Input
2025-11-03 09:00 New York (with London and Tokyo in the zone list)
Expected output
London, UK: 14:00 on Monday, November 3, 2025 / Tokyo, Japan: 23:00 on Monday, November 3, 2025
On that date US daylight saving had ended the day before, so New York is on EST (UTC-5); the UK's daylight saving ended October 26, so London is on GMT (UTC+0); Tokyo is UTC+9 year-round. 09:00 EST equals 14:00 UTC, which is 14:00 in London and 23:00 in Tokyo.
You enter a date, a time, and the zone the time was written in. The tool anchors that input to a single moment, then renders the equivalent local time in every other zone you have added. Adding or removing a zone later re-renders all rows from the same anchor, so every row always describes the same instant.
Each zone's offset on a given day is whatever its daylight saving rules say for that day, and the rules change on dates that differ between countries. Two zones whose transitions fall on different dates drift apart for the weeks in between, and within an hour of a transition the same wall-clock time can occur twice or not at all.
Both cities spring forward and fall back, and in the same direction, so the gap is five hours for most of the year: EST against GMT in winter, EDT against BST in summer. For a few weeks around the US's earlier spring transition and its later autumn transition, one city has switched and the other has not, and the gap is four hours.
That time does not exist in that zone on that date: at 01:00 the clock jumps straight to 02:00. A converter must either reject the input or silently pick a time on one side of the jump, so the result depends on the implementation. Convert 01:00 or 02:00 instead, or anchor on the UTC instant, to get an unambiguous answer.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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