Here are two proposed patches, regarding non-Gregorian calendars in 'date'
(cf. <https://lists.gnu.org/archive/html/bug-gnulib/2025-07/msg00091.html>).
>From 3a7298ccd4c8676f30522745c3cd36d8b1d938cf Mon Sep 17 00:00:00 2001
From: Bruno Haible <br...@clisp.org>
Date: Thu, 17 Jul 2025 16:29:05 +0200
Subject: [PATCH 1/2] date: Force a Gregorian calendar for options --iso-8601
and --rfc-3339
* src/date.c (show_date_helper): Add a use_c_locale parameter.
(batch_convert): Add a format_in_c_locale parameter.
(main): Set format_in_c_locale to true if any of the options --rfc-3339,
--iso-8601, -R is seen.
---
src/date.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)
diff --git a/src/date.c b/src/date.c
index b55aba757..953962820 100644
--- a/src/date.c
+++ b/src/date.c
@@ -37,7 +37,7 @@
#define AUTHORS proper_name ("David MacKenzie")
-static bool show_date_helper (char const *, struct timespec, timezone_t);
+static bool show_date_helper (char const *, bool, struct timespec, timezone_t);
enum Time_spec
{
@@ -336,7 +336,8 @@ adjust_resolution (char const *format)
Return true if successful. */
static bool
-batch_convert (char const *input_filename, char const *format,
+batch_convert (char const *input_filename,
+ char const *format, bool format_in_c_locale,
timezone_t tz, char const *tzstring)
{
bool ok;
@@ -381,7 +382,7 @@ batch_convert (char const *input_filename, char const *format,
}
else
{
- ok &= show_date_helper (format, when, tz);
+ ok &= show_date_helper (format, format_in_c_locale, when, tz);
}
}
@@ -402,6 +403,7 @@ main (int argc, char **argv)
struct timespec when;
bool set_date = false;
char const *format = nullptr;
+ bool format_in_c_locale = false;
bool get_resolution = false;
char *batch_file = nullptr;
char *reference = nullptr;
@@ -451,6 +453,7 @@ main (int argc, char **argv)
XARGMATCH ("--rfc-3339", optarg,
time_spec_string + 2, time_spec + 2);
new_format = rfc_3339_format[i];
+ format_in_c_locale = true;
break;
}
case 'I':
@@ -468,6 +471,7 @@ main (int argc, char **argv)
? XARGMATCH ("--iso-8601", optarg, time_spec_string, time_spec)
: TIME_SPEC_DATE);
new_format = iso_8601_format[i];
+ format_in_c_locale = true;
break;
}
case 'r':
@@ -475,6 +479,7 @@ main (int argc, char **argv)
break;
case 'R':
new_format = rfc_email_format;
+ format_in_c_locale = true;
break;
case 's':
if (set_datestr)
@@ -578,7 +583,8 @@ main (int argc, char **argv)
timezone_t tz = tzalloc (tzstring);
if (batch_file != nullptr)
- ok = batch_convert (batch_file, format_res, tz, tzstring);
+ ok = batch_convert (batch_file, format_res, format_in_c_locale,
+ tz, tzstring);
else
{
bool valid_date = true;
@@ -643,24 +649,25 @@ main (int argc, char **argv)
}
}
- ok &= show_date_helper (format_res, when, tz);
+ ok &= show_date_helper (format_res, format_in_c_locale, when, tz);
}
main_exit (ok ? EXIT_SUCCESS : EXIT_FAILURE);
}
static bool
-show_date_helper (char const *format, struct timespec when, timezone_t tz)
+show_date_helper (char const *format, bool use_c_locale,
+ struct timespec when, timezone_t tz)
{
if (parse_datetime_flags & PARSE_DATETIME_DEBUG)
error (0, 0, _("output format: %s"), quote (format));
- if (format == rfc_email_format)
+ if (use_c_locale)
setlocale (LC_TIME, "C");
bool ok = show_date (format, when, tz);
- if (format == rfc_email_format)
+ if (use_c_locale)
setlocale (LC_TIME, "");
putchar ('\n');
--
2.43.0
>From c9220920335a45c6fdbd9bf0ff2469ddfeb68b96 Mon Sep 17 00:00:00 2001
From: Bruno Haible <br...@clisp.org>
Date: Thu, 17 Jul 2025 16:30:57 +0200
Subject: [PATCH 2/2] date: Update documentation regarding non-Gregorian
calendars
* doc/coreutils.texi (Calendars): New section.
---
doc/coreutils.texi | 86 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 86 insertions(+)
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 7fc2db571..0aad90f22 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -16517,6 +16517,7 @@ is not set. @xref{TZ Variable,, Specifying the Time Zone with
@menu
* Date format specifiers:: Used in @samp{date '+...'}
+* Calendars:: Different concepts of year and month.
* Setting the time:: Changing the system clock.
* Options for date:: Instead of the current time.
@detailmenu
@@ -16839,6 +16840,91 @@ width is also present. Other combinations of flags, field widths and
modifiers are GNU extensions.
+@node Calendars
+@subsection Calendars
+
+@cindex calendar
+A calendar is a system that groups some sequences of days into ``months'',
+and some sequences of months into ``years''.
+In most countries, the calendar in use is the Gregorian calendar,
+with months ranging from January (the first month) to December (the 12th month).
+
+@cindex calendars, non-Gregorian
+In some specific countries, other calendars are in effect, and
+GNU @command{date} supports them in its output.
+The calendar depends on the @code{LC_TIME} category of the current locale:
+@itemize
+@item
+In the locale of Thailand (@code{th_TH.UTF-8}),
+the Thai solar calendar is used.
+@item
+In the locale of Iran (@code{fa_IR}),
+the Persian solar Hijri calendar is used.
+@item
+In the locale of Ethiopia (@code{am_ET}),
+the Ethiopian / Ge'ez calendar is used.
+@end itemize
+
+The dates in these calendars look different.
+For example, the day the GNU project was announced:
+@example
+$ LC_ALL=en_US.UTF-8 date +%Y-%m-%d -d 1983-09-27
+1983-09-27
+$ LC_ALL=th_TH.UTF-8 date +%Y-%m-%d -d 1983-09-27
+2526-09-27
+$ LC_ALL=fa_IR date +%Y-%m-%d -d 1983-09-27
+1362-07-05
+$ LC_ALL=am_ET date +%Y-%m-%d -d 1983-09-27
+1976-01-16
+@end example
+
+In these locales, when a non-Gregorian calendar is in use,
+a few date conversion specifiers should not be used,
+because they don't apply in the expected way:
+@itemize
+@item
+@samp{%C} for the century,
+@item
+@samp{%y} for a two-digit year,
+@item
+@samp{%G} and @samp{%g} for a week-based year,
+@item
+@samp{%U}, @samp{%W}, and @samp{%V} for the week in the year,
+@item
+@samp{%j} for the day in the year,
+@item
+and @samp{%D} for the date in U.S.@: formatting convention.
+@end itemize
+
+If you are using one of these locales
+and want to see Gregorian dates nevertheless,
+you can achieve that by
+@enumerate
+@item
+making sure that you use the @code{LANG} environment variable,
+not the @code{LC_ALL} environment variable,
+for specifiying your general locale, and
+@item
+setting the @code{LC_TIME} environment variable to a locale
+that uses the Gregorian calendar.
+@end enumerate
+@noindent
+For example:
+@example
+$ unset LC_ALL
+$ LANG=fa_IR LC_TIME=en_US.UTF-8 date +%Y-%m-%d -d 1983-09-27
+1983-09-27
+@end example
+
+For more information on how to set your locale, see the GNU gettext manual at
+@ifinfo
+@ref{Users,,The User's View,gettext}.
+@end ifinfo
+@ifnotinfo
+@url{https://www.gnu.org/software/gettext/manual/html_node/Users.html}.
+@end ifnotinfo
+
+
@node Setting the time
@subsection Setting the time
--
2.43.0
