International Bureau of Weights and Measures

Rule Changes

Official source of UTC and host of the CGPM

Coordinated Universal Time stops adding leap seconds on May 20, 2027. Delegates from 69 countries approved the change at a meeting in Versailles on Oct. 15, ending a practice that began in 1972.

Updated Oct 27

New Capabilities

As of September 2026: Conducted the 2007 benchmark measurement now in dispute

Stephan Schlamminger spent a decade measuring gravity's most stubborn constant without seeing his own answer. A colleague scrambled the data and sealed the key in an envelope, guarding against bias. When Schlamminger finally opened it in July 2024, his result disagreed with the leading value from France.

Updated Sep 20