Leap Seconds: Why Our Clocks Sometimes Get an Extra Second
What are leap seconds? Why are they added? And why do we want to abolish them? Everything about the world's most unusual second.
Ever wondered why a minute can sometimes have 61 seconds? The answer is leap seconds – a fascinating phenomenon connecting atomic clocks with Earth's rotation.
What Is a Leap Second?
A leap second is an extra second added to UTC to synchronize highly precise atomic time with Earth's slightly irregular rotation. Our planet doesn't spin perfectly evenly.
Why Do We Need Leap Seconds?
Atomic clocks measure time extremely precisely. Earth's rotation, however, fluctuates – it's gradually slowing due to the Moon's tidal forces. Without leap seconds, UTC would eventually drift from the actual solar day.
- Since 1972, 27 leap seconds have been added
- The last one was on December 31, 2016
- There has never been a negative leap second (removing a second)
The Problem with Leap Seconds
Leap seconds regularly cause problems in the tech world:
- 2012: Reddit, LinkedIn and other services crashed
- 2015: Issues at Twitter, Instagram and Pinterest
- 2017: Cloudflare experienced DNS problems
The issue: software expects 60 seconds per minute. A 61st second can cause crashes, infinite loops, or negative time differences.
The Future: Abolition Decided
In 2022, the General Conference on Weights and Measures voted to abolish leap seconds by 2035. Instead, larger corrections will be made at longer intervals – possibly "leap minutes" in 50–100 years.
Fun Fact
All times on WorldTime.Quest are calculated using the IANA Timezone Database, which accounts for leap seconds and historical changes – ensuring displayed times are always precise.