June Will Be 1 Second Longer

It's a dreaded day for many Internet companies: On June 30, an extra second will be added to the clock, creating the potential to wreak havoc on computer systems not equipped to handle the change. The International Earth Rotation and Reference Systems (IERS) announced an extra second will be added at the end of June to account for a discrepancy between Earth's rotation and the atomic clock. The extra second will be added as the clock strikes midnight universal time, meaning the extra second will come for people in the United States at 8 p.m. EDT. There have been 25 instances since 1972 of an extra second being added.

It's possible that programs not equipped to handle the extra second could have an issue. When the last leap second was added on June 30, 2012, it caused issues with a number of websites, including LinkedIn and Yelp. Mozilla, Reddit and Foursquare all experienced system crashes. Qantas was hard hit, too, with a failure of its check-in system creating flight delays across the network.