The General Conference on Weights and Measures (CGPM) defines the length of a metre.

General Conference on Weights and Measures

International metrological authority

The General Conference on Weights and Measures is the supreme authority of the International Bureau of Weights and Measures (BIPM), the intergovernmental organization established in 1875 under the terms of the Metre Convention through which member states act together on matters…

History of the metre

During the French Revolution, the traditional units of measure were to be replaced by consistent measures based on natural phenomena. As a base unit of length, scientists had favoured the seconds pendulum one century earlier, but this was rejected as it had been discovered that…

September 28

Day of the year

September 28 is the 271st day of the year in the Gregorian calendar; 94 days remain until the end of the year.