Which London observatory gives Greenwich Mean Time its name?

The Royal Observatory in Greenwich gives Greenwich Mean Time its name.

Founded by King Charles II in 1675, the observatory was established to improve astronomy and navigation. Its instruments helped astronomers determine time from observations of stars crossing the Greenwich meridian.

Greenwich became especially important to mariners, who used chronometers set to Greenwich time to calculate longitude. The 1884 International Meridian Conference later recognized the Greenwich meridian as the world’s zero-degree reference, strengthening the observatory’s role in global timekeeping.

A common mix-up is confusing GMT with modern Coordinated Universal Time (UTC). GMT is the historical mean solar time associated with Greenwich; UTC is today’s atomic-clock-based international standard, though the terms are often used casually as synonyms.