- NIST confirmed several public time servers lost their atomic reference signal
- A generator failure interrupted the distribution of America’s primary atomic time scale
- Some NIST servers responded normally while quietly serving inaccurate timestamps
The National Institute of Standards and Technology (NIST) has issued an alert that some of its public time servers may be unreliable.
The advisory focuses on a defined set of hosts, including multiple time-x-b.nist.gov addresses and the authenticated ntp-b.nist.gov service.
According to NIST, these systems may still respond to network requests while no longer referencing a valid atomic time source.
What failed at the Boulder facility
To avoid spreading incorrect data, the agency said it may temporarily take some of the affected hosts offline.
NIST traced the problem to its Boulder, Colorado campus, where a prolonged utility power outage disrupted operations.
The outage occurred during high winds that damaged power lines and triggered safety-related shutdowns.
Although backup power systems were in place, a downstream generator failure interrupted the atomic time scale distribution that feeds the Internet Time Service.
NIST stated that the UTC(NIST) signal drifted by roughly four microseconds during the incident, a deviation that is small but measurable.
The disruption does not affect every NIST time endpoint. Widely used addresses such as time.nist.gov rely on round robin DNS and geographically distributed infrastructure.
This design allows clients to fall back automatically to unaffected locations when one site encounters trouble.
Users who hard-code individual hostnames face greater exposure to localized failures like this one.
Systems running on cloud hosting platforms often rely on pooled or upstream time sources, which can hide short-lived issues at any single facility.
The Boulder site hosts the NIST-F4 atomic clock, which uses cesium atoms to define the length of a second with extreme precision, which underpins services used by telecommunications networks, power grids, financial platforms, and scientific research.
Accurate timing is also fundamental to data center hosting environments, where synchronization affects logging, security protocols, and transaction ordering across distributed systems.
Many enterprise servers trust external authoritative sources, which makes upstream accuracy a shared dependency.
This incident follows another time service disruption earlier in the month at NIST’s Gaithersburg, Maryland, facility, which caused a larger time step error measured in milliseconds, not microseconds.
NIST has not given a firm timeline for full restoration at Boulder and said engineers continue recovery work.
While most consumer systems are unlikely to notice the issue, high-precision users are expected to monitor multiple independent references.
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