The atomic clocks in Boulder, Colorado are back in service. But they could be as much as 5 microseconds off!

That's not much by ordinary standards. It's completely irrelevant for transmitting time on the internet, where millisecond irregularities are common. But it would be 5000 times the usual nanosecond errors.

The good news: nobody is saying the time *has* slipped by 5 microseconds. They're just saying they currently only know it's good to within 5 microseconds.

Jeff Sherman explained how they kept the clocks going despite the fire and power outage:

https://groups.google.com/a/list.nist.gov/g/internet-time-service/c/OHOO_1OYjLY

And then:

"To put a deviation of a few microseconds in context, the NIST time scale usually performs about five thousand times better than this at the nanosecond scale by composing a special statistical average of many clocks. Such precision is important for scientific applications, telecommunications, critical infrastructure, and integrity monitoring of positioning systems. But this precision is not achievable with time transfer over the public Internet; uncertainties on the order of 1 millisecond (one thousandth of one second) are more typical due to asymmetry and fluctuations in packet delay.

NIST provides high-precision time transfer by other service arrangements; some direct fiber-optic links were affected and users will be contacted separately. However, 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 WWV/Ft. Collins campus as a reference standard. This design feature mitigated the impact to many users of the high-precision time signal."