From a47ef9c7168557c0dfdfd003cf970ccd6f25a57c Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Thu, 12 Nov 2020 14:52:22 -0800 Subject: [PATCH] * tz-link.html: Use more systematically. Document "right" seconds better * tz-link.html (Precision timekeeping): Clarify "right" vs "posix" time_t. --- tz-link.html | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/tz-link.html b/tz-link.html index eb4a235..56ef9e4 100644 --- a/tz-link.html +++ b/tz-link.html @@ -1039,14 +1039,16 @@ via an optional "right" configuration where a computer's internal as opposed to the default "posix" configuration where the internal clock ignores leap seconds. The two configurations agree for timestamps starting with 1972-01-01 00:00:00 -UTC (time_t 63 072 000) and diverge for +UTC (time_t 63 072 000) and diverge for timestamps starting with time_t 78 796 800, which corresponds to the first leap second -1972-06-30 23:59:60 UTC in the "right" configuration, and to -1972-07-01 00:00:00 UTC in the "posix" configuration. +1972-06-30 23:59:60 UTC in the "right" configuration, +and to +1972-07-01 00:00:00 UTC in the "posix" configuration. In practice the two configurations also agree for timestamps before 1972 even though the historical situation is messy, partly because -neither UTC nor TAI is well-defined for sufficiently-old timestamps. +neither UTC nor TAI +is well-defined for sufficiently-old timestamps.
  • Leap Smear discusses how to gradually adjust POSIX clocks near a leap second so that they disagree with UTC by at most a @@ -1059,7 +1061,7 @@ cloud service providers. However, according to §3.7.1 of Network Time Protocol Best Current Practices (Internet RFC 8633), leap smearing is not suitable for -applications requiring accurate UTC or civil time, +applications requiring accurate UTC or civil time, and is intended for use only in single, well-controlled environments.
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