[3] RFC 867 - Daytime Protocol, 1/24/2021, 3:35:06 PM, 3/10/2021, 6:22:59 AM https://tools.ietf.org/html/rfc867
[1] NIST Internet Time Service (ITS) | NIST, 1/16/2021, 12:01:31 AM, 1/16/2021, 7:39:36 AM https://www.nist.gov/pml/time-and-frequency-division/time-distribution/internet-time-service-its
[2] ACTS 形式とは少し違う。
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