They say time speeds up as you age. Have you noticed how short a day can be now and things that happened a week ago could have been yesterday?  

Well, that’s a mind thing. But recently, time actually sped up for the planet Earth.  

You probably didn’t notice, but the Earth’s rotation has been slowing down. Until June, that is. 

Earth recorded its shortest day on record, on June 29, completing one rotation in 1.59 milliseconds under 24 hours.  

That’s not much, but it’s got scientists wondering, perplexed and a little worried. They aren’t exactly sure what is causing the slightly faster rotation but speculate it could be linked to climate change, tides, or even the Earth’s layers.  

Irregular rotations create the need for something known as a leap second, a second added to the Coordinated Universal Time (UTC) that keeps our clocks as close to solar time - the movements of the Sun - as possible.  

“If Earth’s fast rotation continues, it could lead to the introduction of the first-ever negative leap second,” a story published on the timeanddate website warned. 

A negative leap second is a second taken away from atomic clocks.  

“This would be required to keep civil time, which is based on the super-steady beat of atomic clocks, in step with solar time, which is based on the movement of the Sun.  

“A negative leap second would mean that our clocks skip one second, which could create potential problems for IT systems,” the timeanddate story said. 

Meta said in a blog post late last month that a negative leap second could have a “devastating effect”.  

In part, that’s because some technological systems have a baked-in assumption that time moves only forward.  

These IT systems are likely to have massive outages if their internal clocks ever need to move back to compensate for an irregularly fast rotation of the Earth.  

“The impact of a negative leap second has never been tested on a large scale. It could have a devastating effect on the software relying on timers or schedulers,” Meta said.  

“Introducing new leap seconds is a risky practice that does more harm than good. We believe it is time to introduce new technologies to replace it,” the post said.  

In 2012, Reddit was inaccessible for up to 40 minutes after an outage caused by a leap second which confused the system’s timer.  

“The leap second and the offset it creates cause issues all over the industry,” Meta wrote. 

A group of scientists - Leonid Zotov, Christian Bizouard and Nikolay Sidorenkov - believe the irregular rotations are caused by the Chandler Wobble. 

The Chandler wobble describes an irregular movement of Earth’s geographical poles across the globe's surface.  

The melting and refreezing of ice caps on the world’s tallest mountains could be contributors. The phenomenon can be visualised by imagining a spinning figure skater slowing down when their arms are outstretched and speeding up as their arms are tucked in. 

For further reading: 7news.com.au