Widely reported, but not yet on Outages: https://groups.google.com/a/list.nist.gov/g/internet-time-service/c/o0dDDcr1... jeff.sherman@nist.gov 2:18 AM (17 hours ago) to Internet-time-service Dear colleagues, In short, the atomic ensemble time scale at our Boulder campus has failed due to a prolonged utility power outage. One impact is that the Boulder Internet Time Services no longer have an accurate time reference. At time of writing the Boulder servers are still available due a standby power generator, but I will attempt to disable them to avoid disseminating incorrect time. The affected servers are: time-a-b.nist.gov time-b-b.nist.gov time-c-b.nist.gov time-d-b.nist.gov time-e-b.nist.gov ntp-b.nist.gov (authenticated NTP) No time to repair estimate is available until we regain staff access and power. Efforts are currently focused on obtaining an alternate source of power so the hydrogen maser clocks survive beyond their battery backups. More details follow. Due to prolonged high wind gusts there have been a combination of utility power line damage and preemptive utility shutdowns (in the interest of wildfire prevention) in the Boulder, CO area. NIST's campus lost utility power Wednesday (Dec. 17 2025) around 22:23 UTC. At time of writing utility power is still off to the campus. Facility operators anticipated needing to shutdown the heat-exchange infrastructure providing air cooling to many parts of the building, including some internal networking closets. As a result, many of these too were preemptively shutdown with the result that our group lacks much of the monitoring and control capabilities we ordinarily have. Also, the site has been closed to all but emergency personnel Thursday and Friday, and at time of writing remains closed. At initial power loss, there was no immediate impact to the NIST atomic time scale or distribution services because the projects are afforded standby power generators. However, we now have strong evidence one of the crucial generators has failed. In the downstream path is the primary signal distribution chain, including to the Boulder Internet Time Service. Another campus building houses additional clocks backed up by a different power generator; if these survive it will allow us to re-align the primary time scale when site stability returns without making use of external clocks or reference signals. Best wishes, -Jeff Sherman