A fierce windstorm swept across Boulder, Colorado, on December 17, 2025, leaving a trail of downed power lines, battered infrastructure, and—unbeknownst to most Americans—a tiny but significant hiccup in the nation’s official timekeeping. The National Institute of Standards and Technology (NIST), home to the country’s most precise atomic clocks and the nerve center for U.S. time standards, found itself at the heart of a rare and complex crisis: the official U.S. time, known as NIST UTC, slipped 4.8 microseconds behind where it should have been. For perspective, that’s just shy of five millionths of a second—an interval so fleeting it’s dwarfed by the 350,000 microseconds it takes a person to blink, as NIST spokesperson Rebecca Jacobson explained to NPR.
But in the world of atomic clocks and digital infrastructure, even a sliver of time can have outsized consequences. According to Tom’s Hardware, the disruption began at approximately 22:23 UTC, when high winds damaged power lines and triggered preemptive shutdowns tied to wildfire risk in the region. The Boulder campus’s primary utility power failed, and, crucially, a standby generator downstream of the signal distribution chain also faltered. This generator was supposed to keep the atomic ensemble time scale—the gold standard for U.S. time—humming along without interruption. Instead, it left the system vulnerable at precisely the moment it needed resilience the most.
As reported by The Register, Jeffrey Sherman, a NIST supervisory physicist whose job description literally involves “watching the clocks all day,” described the aftermath in a mailing list post: “The atomic ensemble time scale at our Boulder campus has failed due to a prolonged utility power outage.” Sherman emphasized that, as a result, the Boulder Internet Time Services no longer had a reliable reference. In a bid to prevent the spread of inaccurate time, he even attempted to disable backup generators powering some of the Network Time Protocol (NTP) infrastructure—essential servers that form the backbone of time synchronization for computers and networks nationwide. Unfortunately, the severity of the storm meant only emergency services personnel could safely access the site, limiting NIST’s ability to intervene directly.
Atomic clocks themselves—cesium beam clocks and hydrogen masers, to be precise—continued ticking away thanks to their own battery backups, as Jacobson told NPR. Yet the real trouble was with the connection between these clocks and the broader measurement and distribution systems. Without a stable power supply, the infrastructure responsible for disseminating official time to the outside world became unreliable. The affected hosts, including time-a-b.nist.gov through time-e-b.nist.gov and ntp-b.nist.gov, were still technically online but no longer referencing a valid or accurate time source. NIST quickly warned users, especially those in telecommunications and aerospace, to switch to alternate sources of time information to avoid cascading problems.
Why does a few microseconds matter? For most people and businesses, the answer is: it doesn’t. “Maybe it’s a bit obtuse to say that four microseconds is both big and small at the same time,” Sherman told NPR. Everyday devices, from smartphones to laptops, would never notice such a minuscule drift. But for critical infrastructure—think GPS navigation, data centers, financial trading platforms, and power grids—precision timing is the invisible glue that keeps everything running smoothly. Any deviation, however tiny, can cause authentication failures between systems, data inconsistencies, or, in the worst case, instability in vital applications.
NIST’s response was swift and transparent. As reported by CBS News, the agency notified "high-end" users—those whose operations depend on microsecond-level accuracy—about the disruption and advised them to tap into the organization’s other geographically distributed time servers. This redundancy is by design: the commonly used time.nist.gov address, for example, relies on round-robin DNS to spread requests across multiple sites, allowing for automatic failover if one location falters. Still, users who had hard-coded specific Boulder-based hostnames into their systems were more exposed to localized failures, underscoring the importance of best practices in network configuration.
Power restoration was not immediate. Local utility Xcel Energy, as cited by The Register, worked through the night of December 20 to bring electricity back to most customers, but NIST’s Boulder site continued to report “Facility outages” and a “< 4.8us clock error” as late as 00:15 MT on December 21. By Saturday evening, crews had managed to restore power to the facility, and NIST engineers began evaluating the damage and correcting the time drift. Yet, as Tom’s Hardware noted, the agency had not provided a firm estimate for when full service would be restored, and the incident followed closely on the heels of a separate Internet Time Service disruption at NIST’s Gaithersburg, Maryland site just a week earlier.
The Boulder incident has prompted renewed scrutiny of the resilience—and funding—of America’s timekeeping infrastructure. Commentators on Tom’s Hardware didn’t mince words, with one observer remarking, “That sounds like they’re probably working with antiquated equipment on a shoestring budget. Given how much IT infrastructure depends on it, it really ought to be bomb-proof, with multiple failovers at each point.” Questions about the adequacy of federal support for NIST and the need for further investment in backup systems and geographical redundancy are now front and center.
Despite the drama, the safeguards built into the nation’s timekeeping system largely did their job. The drift, while real, was quickly identified, contained, and communicated to those who needed to know. As NIST’s own statements and industry best practices underscore, prudent users are expected to monitor multiple independent time sources and configure their systems to fail over automatically when problems arise. For the vast majority of Americans, the episode passed unnoticed. For those who live and work by the tick of the atomic clock, however, it was a stark reminder that even the most precise systems are only as robust as the power and planning behind them.
As dawn broke over Boulder and the hum of servers resumed, NIST’s engineers got back to the business of keeping America on time—down to the microsecond.
