Time on Earth is primarily referenced from the Prime Meridian, a specific line of longitude that serves as the global standard for timekeeping.
The Starting Point for Global Time
The concept of "starting" time globally is tied to the system of time zones. These zones are based on lines of longitude, which circle the Earth vertically from pole to pole. The foundational line for this system is the Prime Meridian, designated as 0 degrees longitude.
According to the reference: "Today, the prime meridian is located in Greenwich, England, but this primary reference line of longitude has not always been at its current location."
Therefore, in the context of international timekeeping and time zones (like Coordinated Universal Time - UTC, or Greenwich Mean Time - GMT), time is said to start or be referenced from the Prime Meridian in Greenwich.
Why Greenwich?
Greenwich was chosen as the location for the Prime Meridian in 1884 at the International Meridian Conference. This was largely due to its significance in maritime navigation, as many ships already used charts based on the Greenwich Meridian. Establishing a single, global reference line simplified navigation and, later, global timekeeping.
Time Zones Explained
Time zones are typically measured in hours ahead of or behind the time at the Prime Meridian (UTC/GMT).
- Areas to the East of the Prime Meridian are ahead of UTC/GMT.
- Areas to the West of the Prime Meridian are behind UTC/GMT.
For instance:
- London, UK (on the Prime Meridian): UTC
- New York, USA (West): UTC-5 (during standard time)
- Tokyo, Japan (East): UTC+9
This system allows for a standardized way to understand and coordinate time across the globe, with Greenwich serving as the crucial starting reference point.
While the concept of time itself is constant everywhere, the measurement and coordination of global time using a standardized system begins with the 0-degree longitude line, which is the Prime Meridian located at the historic Royal Observatory in Greenwich, London, England. You can learn more about its history and significance at places like the Royal Museums Greenwich website.
