UTC — Coordinated Universal Time
The world's primary time standard. UTC+0, no daylight saving, no geographic location — the reference against which every timezone is defined.
UTC in major cities right now
What is UTC?
UTC (Coordinated Universal Time) is the world’s primary time standard — the basis for civil time and all the timezones worldwide. Every timezone on Earth is defined as an offset from UTC: London winter is UTC+0, Tokyo is UTC+9, New York winter is UTC-5, and so on.
Unlike a city’s local time, UTC is not tied to a geographic location and does not observe daylight saving time. It is the same instant everywhere on the planet.
Who uses UTC?
UTC is the reference time for:
- Aviation, shipping, and the military — flight plans, ship logs, and operational orders are all written in UTC to avoid ambiguity
- Internet protocols — server logs, API timestamps, and most computer systems internally store time in UTC
- Scientific research — astronomical observations, satellite data, and global climate measurements are recorded in UTC
- International coordination — multi-timezone meetings, broadcasts, and live events frequently quote times in UTC alongside local time
UTC vs GMT
UTC and GMT (Greenwich Mean Time) are often used interchangeably, and for everyday purposes the difference is invisible: both are UTC+0. But they’re technically distinct. UTC is defined by atomic clocks and adjusted with leap seconds; GMT is defined by the Earth’s rotation at the Greenwich meridian. See the full UTC vs GMT comparison.