The Royal Observatory: Home of Greenwich Mean Time (GMT)

The royal observatory in Greenwich is situated on a hill atop Greenwich park, facing the River Thames. This was where the Greenwich Mean Time (GMT) standard originated from, with the prime meridian line passing through its premises.

 Royal observatory

Just so you know, the prime meridian line is an imaginary line that divides the eastern and western hemispheres of the globe (similar to how the equator divides the northern and southern hemisphere). It has a longitudinal value of 0° and is used as the zero reference point for many countries in the world to keep time on - based on GMT conventions.

Meridian line guide

Furthermore, the prime meridian line was used in many observations relating to astronomy - past and present.

Prime meridian line (0° longitude)

It was pretty cool to see inscriptions around the line showing the longitudinal value of different countries that varied from this particular reference point.

There was also a 24-hour Shepherd gate clock outside the observatory, which was the first ever clock to display the Greenwich Mean Time (GMT) directly to the public.

24-hour shepherd gate clock

The shop was actually selling a replica of this for £150!


If your interested, there's a full audio guided tour throughout the observatory which shows the history of how people from the past made use of astronomy to tell time. There was also an illustration of how the methods evolved from the usage of 'mechanical' gears and gadgets to the technologies we have today.

 Past dial clocks

Being there was definitely an eye opener for me. If I were to ever do any kind of GMT time conversion again, I'd have a greater appreciation of its significance, rather than blindly converting it like before.