Leapsecondssignal

Leapsecondssignal refers to the communications and procedures used to insert a leap second into Coordinated Universal Time (UTC) to keep civil time aligned with the irregular rotation of the Earth. Leap seconds are irregular adjustments issued by the International Earth Rotation and Reference Systems Service (IERS) as part of UTC governance. When a leap second is required, an extra second is added after 23:59:59 on either June 30 or December 31, resulting in the time 23:59:60 before returning to 00:00:00.

The leap second signal is disseminated through official IERS bulletins, ITU-R recommendations, and is encoded into various timekeeping and navigation systems such as NTP, GPS, and PTP. In practice, different systems implement the signal in different ways: some adjust their local clocks by pausing for one second, while others use methods like leap smear to distribute the adjustment more gradually over a period of time. The leap-second signal must be properly handled by software and hardware timekeepers, as well as by logging systems and network protocols, to avoid timekeeping or synchronization errors.

Contemporary discussions address whether leap seconds should remain part of UTC or be replaced by a continuous time scale. IERS and ITU-R continue to evaluate options, but as of the latest updates, leap seconds remain an official feature of UTC, and the leap-second signal continues to be issued when needed.