A critical power failure at a US government laboratory last week caused the nation's official timekeeping signal to slow down by a fraction of a second, a time watchdog has confirmed.
How a Storm Disrupted Atomic Precision
A severe windstorm on 17 December knocked out mains power at the Denver laboratory of the National Institute of Standards and Technology (NIST). The facility's backup generator then failed, disrupting systems vital for maintaining the Coordinated Universal Time (UTC) signal disseminated by the United States.
The official time is calculated as a weighted average of signals from NIST's 16 ultra-precise atomic clocks. These devices use the natural resonant frequencies of atoms to measure time with extraordinary accuracy. The power disruption meant these clocks fell out of sync with the systems that measure and broadcast the official time standard.
The Scale of the Time Slip
NIST spokesperson Rebecca Jacobson stated in a public email that the incident resulted in the NIST UTC time scale slowing down by 4.8 microseconds, or five millionths of a second. To put this minuscule deviation into perspective, it takes a human about 350,000 microseconds to blink an eye.
While battery backups kept the individual atomic clocks running, the sync between them and the dissemination systems was lost. NIST said it acted swiftly to restore backup power by activating a reserve diesel generator. "We regained some monitoring ability, showing that the disseminated UTC signal likely did not deviate by more than 5 us (five millionths of a second) and appeared stable," Ms Jacobson explained.
Implications for Critical Systems
Although the deviation was too small for most organisations to notice, it could be significant for high-end systems that depend on nanosecond precision. These include:
- Global Positioning System (GPS) and satellite navigation networks.
- Telecommunications infrastructure.
- High-frequency financial trading platforms.
Jeff Sherman, a NIST group leader, emphasised that such precision is crucial for scientific applications, critical infrastructure, and integrity monitoring of positioning systems. However, he noted that a backup feature mitigated the impact for many users. "The most popular method based on common-view time transfer using GPS satellites as 'transfer standards' seamlessly transitioned to using the clocks at NIST's Ft. Collins campus as a reference standard," he said in an email.
The institute immediately informed reliant organisations to reference other time sources during the outage, ensuring minimal disruption to services that depend on the world's most accurate timekeeping.
