UTC

Coordinated Universal Time, the agreed-upon baseline for the world's timezones. The mismatched initialism avoids favouring any particular language.

It is technically a refinement of what remains widely known as GMT, Greenwich Mean Time, being the solar time at an observatory in Greenwich, England, which became prominent in the Age of Exploration. Conveniently, the antipodal longitude, where the international date line must be defined, is in the relatively sparsely populated Pacific Ocean.

Abbreviated Z in the single-letter military time zone system, the corresponding name Zulu is widely used.

The technical differences between UTC, GMT and variants such as UT0 are meaningful to such fields as astronomy.