The Greenwich Meridian was first established by the first Astronomer Royal of Great Britain, John Flamsteed, in 1675. In 1725 Greenwich Meridian modified by the second Astronomer Royal, Edmond Halley, It was adjusted again in 1750 by James Bradley, the third Astronomer Royal, and in 1851 by George Airy (1801-1892), the fourth Astronomer Royal (1835-1881).

     In 1884 25 countries at The International Meridian Conference in Washington, D.C. established Airy’s meridian as the zero or prime meridian for calculating longitude

     The stamp issued by Tonga in 1984 commemorates the centenary of the Washington conference, at which the Greenwich Meridian received international recognition, with a portrait of George Airy and a double globe showing the Prime Meridian and the Anti-Meridian in red on the double globes.