Leap Second

A leap second is a one-second adjustment that is occasionally added to Coordinated Universal Time (UTC) to accommodate the irregular rotation of the Earth. Unlike leap years, which follow a regular pattern, leap seconds are inserted irregularly based on astronomical observations.

The Earth's rotation is gradually slowing due to tidal friction and other factors, making the mean solar day slightly longer than 86,400 seconds (the number of SI seconds in a standard day). To keep UTC within 0.9 seconds of UT1 (the time standard based on Earth's rotation), leap seconds are added when necessary.

Since their introduction in 1972, leap seconds have typically been added at a rate of about one every 18 months, though the frequency varies. They are usually scheduled for June 30 or December 31, where 23:59:59 is followed by 23:59:60 before rolling over to 00:00:00 of the next day.

Leap seconds pose challenges for computer systems, which often aren't designed to handle a 61-second minute. Various strategies exist for implementing leap seconds in computing: - Smearing the extra second over a longer period - Handling the extra second as a special case - Stepping the clock backward after the leap second

Due to these complications, there have been proposals to eliminate leap seconds in favor of allowing UTC to gradually drift from UT1, with occasional larger adjustments made after much longer intervals.