Australia's corporate regulator is warning the addition of a leap second to 2015 could cause havoc for the stock market and IT companies.

On June 30 at 11:59.59pm (GMT), an extra second will be added so the Earth's rotational spin can catch up with the world's atomic clocks.

But while the idea of an extra second in the day might seem small, computer security expert Dr Suelette Dreyfus warned the consequences could be significant.

"The last time a leap second was added was on June 30, 2012 and that did cause some technical problems for popular websites like Reddit and Mozilla and LinkedIn," she said.

"I understand that Qantas computer systems went down for a period of time partially because of it.

"So is it going to be the end of the world as we know it? 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."

That risk has prompted the Australian Securities and Investments Commission (ASIC) to issue a warning on its website.

It urged financial market stakeholders to review their IT systems in order to address any unwelcome impacts.

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"I think ASIC's warning is a really good idea because it's just basically saying, 'Heads up everybody, you need to stop and think about whether or not this leap second is going to cause problems for the type of business that you're in'," Dr Dreyfus said.

"If you're building pools in people's backyards then it's probably not going to be such an issue for your company.

"If you're doing complex trades second by second in currencies or commodities, it might actually be an issue."

End of the leap second?

There have been 25 leap seconds since they were introduced in 1972, but they could soon be lost to time.

The world's governments are due to vote on whether to abolish the leap second at the World Radiocommunications Conference in Geneva in November.

Dr Fred Watson, an astronomer with the Australian Astronomical Observatory, said the Moon was the reason the Earth was slowing down.

"It all comes about because of the tides. The tides essentially use up energy and it's the Earth's rotational energy that is lost," he said.

"That actually goes to the Moon. In fact, it's what is driving the Moon to move very slowly further away from the Earth at about 3.5 centimetres per year."

Supporters of the leap second argue corrections are needed to maintain accurate time for some branches of science.

Those opposed say it is not worth the energy to change the clocks infrequently and that it will be beneficial for computing to have a timescale that never needed changing.

Without leap seconds there would be a slip of two to three minutes by 2100 and about half an hour by 2700.