Definition

1. Noun:
   • A one-second adjustment to Coordinated Universal Time (UTC): A "leap second" is a positive or negative one-second increment applied to the UTC time scale. Its primary purpose is to keep atomic time (TAI) closely synchronized with astronomical time (UT1), which is based on the Earth's variable rotational speed.

Usage

• The term is used in the context of timekeeping, astronomy, and global navigation systems to describe the scheduled correction.
• It functions as a countable noun (e.g., , , ).

Examples

• Noun:
  • A leap second was added at the end of June 2015.
  • The International Earth Rotation and Reference Systems Service (IERS) announces when a leap second is necessary.
  • Some computer systems experience issues when a leap second occurs.

Advanced Usage

• "to introduce a leap second": To formally implement the one-second adjustment into the official time standard.
  • The decision to introduce a leap second is made based on observations of the Earth's rotation.
• "leap second adjustment": The process or event of applying the correction.
  • The network is tested for its handling of the leap second adjustment.

Variants and Related Words

• UTC (Coordinated Universal Time): The primary time standard to which leap seconds are applied.
• TAI (International Atomic Time): The continuous atomic time scale from which UTC diverges by integer seconds.
• UT1 (Universal Time): A measure of time based on the Earth's rotation, which UTC approximates.

Synonyms

• Time correction: A general term for an adjustment made to a timekeeping system. (Note: "Leap second" is a very specific type of time correction.)

Related Phrases

• Leap second event: The specific moment in time when the adjustment is made.
  • Engineers prepared the servers for the upcoming leap second event.
• Positive leap second: The addition of one second (23:59:60 is inserted).
• Negative leap second: The subtraction of one second (23:59:58 would follow 23:59:57). This has never been implemented.

Notes

• Leap seconds are necessary because the Earth's rotation is gradually slowing down, though at an irregular rate. This causes astronomical days (based on Earth's rotation) to be slightly longer than the precisely constant atomic days.
• The adjustment is typically added on June 30 or December 31. During a positive leap second, the time sequence is: 23:59:59, 23:59:60, 00:00:00.

Noun

1. a second (as measured by an atomic clock) added to or subtracted from Greenwich Mean Time in order to compensate for slowing in the Earth's rotation