In June, one second will be added to the atomic clocks that keep exact track of time, an act that could cause some trouble for computer systems.

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The extra second is occurring  because we keep track of days, months and years by measuring how long it takes the earth to rotate on its axis - 24 hours. However, it turns out the earth's spin is slowing down, by about two thousandths of a second per day, and that means it's not keeping up with atomic clocks. In order to keep pace with atomic clocks, an extra second has to be added about every four years.

"If we didn't do this, we'd end up after a long period of time with noon time happening after dark and things like that, so we have to keep the two synchronized," said David Loudon, owner of Shadow Services, a computer networking firm.

The extra second will be added on June 30 at 11:59 p.m. in Greenwich, England.

When the extra second is added, Loudon said it's possible some computer programs that keep track of time may get mixed up.

"When that happens, (adding the extra second) some programs don't handle it well. They get a little confused, they get very slow - sometimes they stop operating altogether," Loudon said.

For this reason, Loudon suggested putting off certain tasks on June 30. "I probably wouldn't do anything that's mission critical. I mean I probably wouldn't do my banking at 7:00 p.m. at night."

And while some computers may have difficulty with the extra second, it's not something that should permanently cripple them.

Loudon said a simple reboot of the server should fix any problem that comes up, and any reputable Internet service should be able to handle the situation.

"If there's going to be a problem it's going to happen pretty quickly after that time, and it should recover pretty quickly too," Loudon said.

When this same situation happened four years ago, there were some glitches, but nothing major went wrong.