Time Zone Converter: Convert a Date and Time Between 40 Cities

How time zone conversion works and why the date matters

Every time zone is defined as an offset from Coordinated Universal Time (UTC). New York is UTC-5 in winter, London is UTC+0, and Tokyo is UTC+9. To convert, the tool turns your local time into a single UTC moment, then writes that moment as a clock reading in the second city. The worked example on this page starts at 9:00 AM in New York on December 1, 2026. That is 14:00 UTC, which is 2:00 PM in London, five hours ahead.

Daylight saving time is why the same two cities can be four hours apart in March and five hours apart in December. The United States and Europe switch on different weekends, so a few weeks each spring and fall the gap shifts by an hour. This converter asks your browser for the rules that apply on the exact date you enter, so it gets those odd weeks right. It also flags when a zone is on daylight time, and warns when your start time falls in the hour that clocks skip forward.

The date can change as well. Convert 9:00 PM in Los Angeles to Tokyo and the answer lands on the next calendar day, 17 hours ahead. The result lists the converted date and says whether it is the same, next or previous day. Half-hour zones such as India at UTC+5:30 are handled too. Planning a flight? Pair this with the flight time calculator and the jet lag calculator.

Reference table: standard (non-daylight) offsets for common cities. The table is plain HTML so it stays visible without JavaScript.

Where these numbers come from

The formulas and default values in this calculator are based on:

• IANA Time Zone Database city names, applied through the JavaScript Intl.DateTimeFormat API in your browser
• UTC offsets in the table are standard-time values. Note: offsets change when governments change daylight saving law, so confirm travel-critical times with your airline or host

This is a planning estimate, not medical, legal or immigration advice. Fees, allowances, limits and entry rules change, so confirm the figures with your airline, cruise line, customs agency or the official government source before you book or travel, and follow their rules if they differ from this page.