On 5/7/23 07:52, Andreas Schwab wrote:
Thus TZ=UTC+2 means two hours before UTC.
Yes, and this mistake seems to be common enough that I installed the
attached patch into Gnulib, so that it'll propagate into the Coreutils
manual, which should help people who read the 'date' documentation
(admittedly only a subset of 'date' users).
From 9f205ff9624b8e10b4331432c59bc732b8c1a7fe Mon Sep 17 00:00:00 2001
From: Paul Eggert <egg...@cs.ucla.edu>
Date: Sun, 7 May 2023 09:28:57 -0700
Subject: [PATCH] Warn against bogus TZ settings
* doc/parse-datetime.texi (Specifying time zone rules):
Warn against TZ="UTC=5".
---
ChangeLog | 6 ++++++
doc/parse-datetime.texi | 3 +++
2 files changed, 9 insertions(+)
diff --git a/ChangeLog b/ChangeLog
index 06ff163e0e..823d32b66f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2023-05-07 Paul Eggert <egg...@cs.ucla.edu>
+
+ Warn against bogus TZ settings
+ * doc/parse-datetime.texi (Specifying time zone rules):
+ Warn against TZ="UTC=5".
+
2023-05-05 Bruno Haible <br...@clisp.org>
dirfd: Add tests.
diff --git a/doc/parse-datetime.texi b/doc/parse-datetime.texi
index d54d7660c8..ec0160da8e 100644
--- a/doc/parse-datetime.texi
+++ b/doc/parse-datetime.texi
@@ -574,6 +574,9 @@ This example uses the somewhat-confusing POSIX convention for rules.
and the time zone is 7 hours west of Greenwich, and
@samp{TZ="<+0530>-5:30"} says that the time zone abbreviation is @samp{+0530}
and the time zone is 5 hours 30 minutes east of Greenwich.
+(One should never use a setting like @samp{TZ="UTC-5"}, since
+this would incorrectly imply that local time is five hours east of
+Greenwich and the time zone is called ``UTC''.)
Although trickier POSIX @env{TZ} settings like
@samp{TZ="<-05>+5<-04>,M3.2.0/2,M11.1.0/2"} can specify some daylight
saving regimes, location-based settings like
--
2.40.1
