Time Zone Converter

Formula

How this is calculated

You choose a "from" city, a date and a time, and a "to" city. The tool first converts your entered wall-clock time into a single universal instant (UTC) by subtracting the from-city's UTC offset for that date, then re-expresses that same instant in the to-city's local time by adding its UTC offset. Because the conversion goes through one absolute moment, both cities always refer to the exact same instant — only the clock reading differs.

Offsets are read live from the browser's IANA time-zone database via the Intl API, so daylight-saving time (DST) is handled automatically: a city's offset can change by an hour across the year, and the converter uses the offset that applies on the date you pick. The time difference shown ("X hours ahead/behind") is simply the gap between the two offsets at that moment.

The globe places each city by its latitude and longitude using an orthographic projection, draws the great-circle path between them, and shades the planet from the position of the Sun (the subsolar point) for your chosen instant — so you can see at a glance which city is in daylight and which is at night.