格林尼治时间以英国首都伦敦市郊格林尼治天文台命名，作为全球通用的时间参考标准已使用120多年。如今，这一以地球自转为依据的“世界时”可能由以原子振荡周期为依据的“原子时”彻底取代。

For more than 120 years, Greenwich Mean Time (GMT) has been the international standard for timekeeping, but it is now under threat from a new definition of time itself based not on the rotation¹ of the Earth, but on atomic clocks.

In January the International Telecommunication² Union will meet in Geneva to vote on whether to adopt the new measure, despite protests from Britain.

The two-day meeting of about 50 experts at a country house north-west of London, under the aegis³ of（在……支持下） the prestigious⁴ Royal Society, on Thursday and Friday will look at some of the issues involved.

Predictably the question has hurt Britain's national pride - particularly when the British believe their old rivals France are leading the push to change from GMT to the new time standard.

"We understand that in Britain they have a sense of loss for GMT," said Elisa Felicitas Arias⁵, director of the time department at the France-based International Bureau of Weights and Measures (BIPM), which pushed for the change.

GMT is based on the passage of the Sun over the zero meridian⁶ line（子午线） at the Greenwich Observatory⁷ in southeast London, and became the world standard for time at a conference in Washington in 1884.

France had lobbied for Paris Mean Time at the same conference.

In 1972 it was replaced in name by Universal Coordinated⁸ Time (UTC) but that essentially⁹ remained the same as GMT.

UTC is based on about 400 atomic clocks at laboratories around the world but then corrected with "leap seconds" to align¹⁰ itself with the Earth's rotational¹¹ speed, which fluctuates.