What is Greenwich Mean Time

Discover the origins and significance of Greenwich Mean Time, the standard for timekeeping worldwide. Learn about its history, usage, and benefits in this comprehensive guide.


Greenwich Mean Time (GMT) is a time system originally referring to Mean Solar Time at the Royal Observatory in Greenwich, London. It has served as the world’s time standard since 1884.

History of GMT

GMT was established to aid navigation and is based on the Sun’s position in the sky, marking noon when the Sun is at its highest point. It was first used by sailors to determine their position at sea.

Usage of GMT

GMT is no longer used as a civil time standard, but it is still the basis for Coordinated Universal Time (UTC), which is used worldwide as the standard for timekeeping in many areas.

Greenwich Meridian Line

The Prime Meridian at the Royal Observatory marks the starting point for measuring longitude and is where GMT is calculated from. It is a popular tourist attraction and a symbol of GMT’s influence.

Benefits of GMT

  • Global Standardization: GMT provides a universal reference point for timekeeping across different regions.
  • Historical Significance: GMT has a rich history in navigation and exploration, making it an important part of human achievement.
  • Accuracy: GMT is based on astronomical observations, ensuring precise time measurement.

Case Study: International Business

For international businesses operating across multiple time zones, GMT serves as a common reference point for scheduling meetings and coordinating activities. By using GMT as a standard, companies can avoid confusion and streamline operations.


According to a survey, 80% of international air travel schedules are based on GMT for coordinating arrivals and departures.


Greenwich Mean Time has played a vital role in standardizing timekeeping globally and continues to be a significant reference point for various industries and activities.

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