Final update on Dec. 19 incident at Boulder site

[jeff.s...@nist.gov]

Dear colleagues,

By 22:24 UTC (3:24 pm MST) on Sunday, Dec 21, NIST staff brought the offset of UTC(NIST) from UTC to the level of a few nanoseconds (billionths of a second), which is well within the normal range of precision for this system. This re-alignment was achieved using a backup time scale system at NIST Boulder. Assessment and other service repairs continue, but UTC(NIST) as furnished to the Boulder Internet Time Service is now providing accurate time.

We have determined that during the backup-power outage, the UTC(NIST) signal provided to the Boulder Internet Time Service did not deviate by more than 5 microseconds (five millionths of one second). As the typical uncertainty of time transfer over the public Internet is on the order of one millisecond (1/1000th of a second), we can say in retrospect that the accuracy of the Internet Time Service was not compromised and that users were not impacted by the time deviation.

Project email: internet-t...@nist.gov