How a Power Outage In Colorado Caused US Official Time To Be 4.8 Microseconds

Tony Isaac shares a report from NPR: The U.S. government calculates the country's official time using more than a dozen atomic clocks at a federal facility northwest of Denver. But when a destructive windstorm knocked out power to the National Institute of Standards and Technology (NIST) laboratory in Boulder on Wednesday and a backup generator subsequently failed, time ever so slightly slowed down. The lapse 'resulted in NIST UTC [universal coordinated time] being 4.8 microseconds slower than it should have been,' NIST spokesperson Rebecca Jacobson said in an email.

Since 2007, the official time of the U.S. has been determined by the commerce secretary, who oversees NIST, along with the U.S. Navy. The national time standard is known as NIST UTC. (Somewhat confusingly, UTC itself is a separate, global time standard to which the U.S. and other countries contribute measurements.) NIST currently calculates the standard using a weighted average of the readings of 16 atomic clocks situated across the Boulder campus. Atomic clocks, including hydrogen masers and cesium beam clocks, rely on the natural resonant frequencies of atoms to tell time with extremely high accuracy.

All of the atomic clocks continued ticking through the power outage last week thanks to their battery backup systems, according to NIST supervisory research physicist Jeff Sherman. What failed was the connection between some of the clocks and NIST's measurement and distribution systems, he said. Some critical operations staff who were still on site following the severe weather were able to restore backup power by activating a diesel generator the team had kept in reserve, Sherman said.

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