International Earth Rotation and Reference Systems Service (IERS)

Rule Changes

Monitors Earth's rotation and the UTC-UT1 difference

Delegates from 69 countries voted Thursday in Versailles to abolish the leap second. Starting May 20, 2027, Coordinated Universal Time (UTC) will run continuously, and Earth's rotation will be allowed to drift up to a full hour from atomic time before a leap hour resets it.

Updated Yesterday