According to research,
Greenwich, England has been the home of Greenwich Meridian Time (GMT) since 1884. GMT is sometimes called Greenwich Meridian Time because it is measured from the Greenwich Meridian Line at the Royal Observatory in Greenwich. Greenwich is the place from where all time zones are measured.The
Greenwich Meridian marks the starting point of every time zone in the World. GMT is Greenwich Meridian Time is the mean time that the earth takes to rotate from noon-to-noon.
GMT is World Time and the basis of every world
time zone which sets the time of day and is at the centre of the time zone map. GMT sets current time or official time around the globe. Most time changes are measured by GMT. Although GMT has been replaced by atomic time it is still widely regarded as the correct time for every international time zone.