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https://www.ntp.org/documentation/drivers/driver24/
USNO Modem Time Service
Jun 27, 2022 - Overview of the USNO Modem Time Service reference clock driver.
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https://www.nist.gov/pml/time-and-frequency-division/time-services/nist-usno/nist-usno-2022-archive
NIST USNO 2022 Archive | NIST
Jan 2, 2026 - UTC (USNO) - UTC (NIST) The United States Naval Observatory (USNO) and the National Institute of Standards and Technology (NIST
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