What Is a Leap Second?
A leap second is a one-second adjustment occasionally added to Coordinated Universal Time (UTC) to keep it close to time based on Earth’s rotation, which is slightly irregular. Leap seconds have been added 27 times since 1972. In 2022, international timekeeping authorities decided to stop adding them by 2035.
Why They Cause Problems
Computer systems often assume every minute has 60 seconds, so an extra second has caused software errors.
Leap Second vs. Leap Year
A leap year adds a day to keep the calendar aligned with Earth’s orbit; a leap second aligns clocks with Earth’s rotation.
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🔗 Related Terms
More Time & Dates Terms
- 24-Hour Clock (Military Time)
- Business Days
- Calendar Quarter
- Chronological Age
- Day of the Year
- Daylight Saving Time (DST)
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Last updated: September 29, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.