From 42df6286d5f5a44dbf2f89eb9dc84697310a257a Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Fri, 2 Dec 2016 09:32:14 -0800 Subject: [PROPOSED] * Makefile, NEWS, tz-link.htm: Mention leap smearing. --- Makefile | 13 ++++++++----- NEWS | 7 +++++++ tz-link.htm | 25 ++++++++++++++++++------- 3 files changed, 33 insertions(+), 12 deletions(-) diff --git a/Makefile b/Makefile index 1b714a8..6ce3483 100644 --- a/Makefile +++ b/Makefile @@ -72,11 +72,11 @@ MANDIR= $(TOPDIR)/man LIBDIR= $(TOPDIR)/lib -# If you always want time values interpreted as "seconds since the epoch -# (not counting leap seconds)", use +# If you want only POSIX time, where time values interpreted as +# seconds since the epoch (not counting leap seconds), use # REDO= posix_only -# below. If you always want right time values interpreted as "seconds since -# the epoch" (counting leap seconds)", use +# below. If you want want only "right" time, with values interpreted +# as seconds since the epoch (counting leap seconds), use # REDO= right_only # below. If you want both sets of data available, with leap seconds not # counted normally, use @@ -85,7 +85,10 @@ LIBDIR= $(TOPDIR)/lib # normally, use # REDO= right_posix # below. POSIX mandates that leap seconds not be counted; for compatibility -# with it, use "posix_only" or "posix_right". +# with it, use "posix_only" or "posix_right". POSIX time is often combined +# with leap smearing, as this is more accurate than strict POSIX time +# and it often works better than "right" time with applications that +# are not leap second aware. REDO= posix_right diff --git a/NEWS b/NEWS index af1cdb1..30756cb 100644 --- a/NEWS +++ b/NEWS @@ -1,5 +1,12 @@ News for the tz database +Unreleased, experimental changes + + Changes to documentation and commentary + + tz-link.htm now covers leap smearing, which is popular in clouds. + + Release 2016j - 2016-11-22 23:17:13 -0800 Briefly: Saratov, Russia moves from +03 to +04 on 2016-12-04. diff --git a/tz-link.htm b/tz-link.htm index 49fde11..9c92ca6 100644 --- a/tz-link.htm +++ b/tz-link.htm @@ -10,7 +10,7 @@ content="Sources for time zone and daylight saving time data"> - + LGPL. implementation of a binary file reader. It is freely available under the Apache License.
  • CCTZ is a simple C++ -library that translates between UTC and civil time and can read binary -files. It is freely available under the Apache License.
    • +library that translates between UTC and civil time and +can read binary files. It is freely available under the Apache +License.
  • ZoneInfo.java is a tz binary file reader written in Java. It is freely available under the LGPL.
    • @@ -805,20 +806,30 @@ how the art has progressed over the past few decades. href="https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html">IERS Bulletins contains official publications of the International -Earth Rotation and Reference Systems Service, which decides -when leap seconds occur. +Earth Rotation and Reference Systems Service, which decides when leap +seconds occur. The tz code and data support leap seconds +via an optional "right" configuration, as opposed to the +default "posix" configuration. +
  • Leap Smear +discusses how to gradually adjust POSIX clocks near a +leap second so that they disagree with UTC by at most a +half second, even though every POSIX minute has exactly +sixty seconds. This approach works with the default tz +"posix" configuration, and has become popular among cloud +service providers.
  • The Leap Second Discussion List covers McCarthy -and Klepczynski's proposal to discontinue leap seconds, +and Klepczynski's 1999 proposal to discontinue leap seconds, discussed further in The leap second: its history and possible future. UTC might be redefined without Leap Seconds gives pointers on this -contentious issue.
    • +contentious issue, which was active until 2015 and could become active +again.

    Time notation