NIST warns that several of its Internet Time Service servers may report inaccuracies due to power outage – Boulder servers ‘no longer have true time reference’

The National Institute of Standards and Technology warned that several of its Internet Time Service servers may give wrong time following the failure of the NIST-F4 core atomic timescale at the Boulder, Colorado campus. The alert was posted on the NIST Internet Time Service public mailing list after an extended power outage disrupted the facility on December 17, with engineers still working to fully restore normal operations several days later.

According to NIST, the Boulder campus lost power around 10:23 p.m. UTC during a period of high winds that caused line damage and precautionary shutdowns related to the risk of wildfires in the region. Although the backup systems were expected to maintain continuity, NIST says the critical failure of the backup generator occurred downstream of the signal distribution chain that powers the Internet Time Service infrastructure in Boulder. As a result, the nuclear assembly time scale on which these services rely has been broken.

The warning clearly lists the affected hosts from time-ab.nist.gov to time-eb.nist.gov along with ntp-b.nist.gov, which is used for NTP authentication. NIST cautioned that while servers may still respond to network requests, they may not reference a valid and true time source. The agency said it may disable these hosts completely to prevent the risk of customers being allocated the wrong time.

This incident does not appear to have affected all NIST time services. For example, the commonly used address time.nist.gov relies on round-robin DNS across multiple geographically distributed servers, allowing clients to automatically fail over when one site experiences problems. However, users who hardcode individual hostnames may be more susceptible to localized failures such as this.

In a statement to local media, a NIST spokesman said the disruption caused a brief interruption during generator switching and an offset of UTC(NIST) time by about four microseconds. For most consumer and enterprise systems, this level of error would not be noticeable, but users requiring high precision – such as scientists or finance – are typically expected to monitor multiple independent time sources and receive alerts through established channels.

The NIST-F4 atomic clock in Boulder uses cesium atoms to measure the precise length of a second, which is only a little more sophisticated than the clock you could build on the Pi. It is an vital reference point used in many applications such as GPS systems, data centers, telecommunications and power generation, all of which require extremely precise time measurement. According to NIST, it is the “gold standard for accuracy” in time measurement.

The Boulder incident follows another disruption of Internet time service that occurred on December 10 at the NIST headquarters in Gaithersburg, Maryland, where a failure of an atomic time source resulted in a time step of approximately minus 10 milliseconds on affected hosts. As of this writing, NIST has not provided an exact estimate of when full service will be restored on the Boulder campus.

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