LOS ANGELES – The planet’s timekeepers added an extra second to the clock at midnight universal time Saturday night. But if you blinked, you just might have missed it.

The so-called leap second was needed to synchronize the world’s official atomic clocks, said John Lowe, who heads the time and frequency services group at the National Institute of Standards and Technology.

The reason? Earth is spinning just a bit slowly. The time it takes Earth to rotate on its axis – the very definition of a day – is about two milliseconds longer than it was 100 years ago, said Geoff Chester, spokesman at the U.S. Naval Observatory, in an interview with the Associated Press.

Over the course of a year, that adds up to nearly three-quarters of a second.

A second might not seem like much, Lowe said in an interview with the Los Angeles Times. “But if you allow that accumulation to go on, it starts to become apparent.” The seconds would stack up and “sunrise” would eventually take place at sunset. And “spring” would arrive in the dead of winter, Lowe said.

“Soon you’d have an obvious problem,” he said.

It’s up to the International Earth Rotation and Reference Systems Service to coordinate such leap seconds, and such coordination typically takes place in either June or December. Hence, this weekend’s skip: Universal time was 11:59:59 and then the rarely seen 11:59:60 before the clocks struck midnight.

When asked what he planned to do with his extra second, Lowe responded:

“I am going to observe it by making sure that all our broadcast services take effect,” he said.