For just one second on June 30, 2015 - time will literally stand still.

Because next month, the world will experience a unique event in astrophysics known as a 'leap second'.

They happen occasionally to compensate for the slowing of the Earth's rotation.

And this year, an extra second will be added at 00.59.60 on June 30.

This allows the world's clocks to catch up with the Earth and make sure they are as accurate as possible.

In Britain, it will happen just before 1am as we are one hour ahead of Coordinated Universal Time (UTC).

Has this ever happened before?

Yes. Leap seconds were first introduced in 1972 and there have been 25 instances of one being introduced.

The most recent was in 2012, and reports suggested it played havoc with the internet.

Websites including Reddit, Yelp, LinkedIn went down for a period of time.

There are fears the same could happen again and stock markets are also wary of mishaps, particularly in Australia.

The leap second will happen at 10am on July in Australia, just as the stock exchange is opening.

"Is it going to be the end of the world as we know it?" Suelette Dreyfus, computer security expert, told ABC News.

"Probably not, but for companies that haven't actually spent some time thinking through what it might mean for their systems, there is a risk that things could go astray."

Airports and airlines could also face problems with check-in computers.

But who is 'in charge' of time?

It may come as a surprise to Dr Who fans, but the real Time Lords of the universe can be found in an observatory in Paris.

Here you will find the International Earth Rotation and Reference Systems Service (IERS) - the body responsible for administering global time.

In January, they sent out what may be one of the greatest bulletins ever, addressed to "authorities responsible for the measurement and distribution of time."

In a casual tone, head of the IERS Dr Daniel Gambis announced that a "positive leap second" will be added to Coordinated Universal Time (UTC) on June 30.

For those who didn't know, UTC is the international time standard which regulates clocks around the world.

It is based around atomic time, a method of measuring time based on the frequency of vibrations within an atom.

What would happen if we didn't have a leap second?

The leap second has some vocal opponents, particularly among web businesses for the reasons mentioned above.

But the scientific community says it is essential for research purposes.

Members of the International Telecommunications Union, which sets the world's clocks will meet later this year to decide whether to scrap leap seconds once and for all.

If we did, experts have suggested we could slip up to three minutes ahead of time by 2100, and about half an hour by 2700.

Originally published on Mirror Online.