From d82d038b5475a14d2210925bac9d949774a4531c Mon Sep 17 00:00:00 2001
From: Krishna Nagam <40730166+KrishnaNagam@users.noreply.github.com>
Date: Sun, 12 Jan 2025 20:02:31 -0500
Subject: [PATCH] date: display %Z alphabetic time zone abbreviation

Improve the display of dates formatted with the `%Z` specifier so that
the timezone abbreviation is displayed, not just its numeric offset.

Fixes #3756

Co-authored-by: Jeffrey Finkelstein <jeffrey.finkelstein@protonmail.com>
---
 src/uu/date/src/date.rs    | 21 ++++++++++++++++++---
 tests/by-util/test_date.rs | 16 ++++++++++------
 2 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/src/uu/date/src/date.rs b/src/uu/date/src/date.rs
index 766e79bd4..d91f8f82c 100644
--- a/src/uu/date/src/date.rs
+++ b/src/uu/date/src/date.rs
@@ -6,10 +6,12 @@
 // spell-checker:ignore (chrono) Datelike Timelike ; (format) DATEFILE MMDDhhmm ; (vars) datetime datetimes
 
 use chrono::format::{Item, StrftimeItems};
-use chrono::{DateTime, FixedOffset, Local, Offset, TimeDelta, Utc};
+use chrono::{DateTime, FixedOffset, Local, Offset, TimeDelta, TimeZone, Utc};
 #[cfg(windows)]
 use chrono::{Datelike, Timelike};
+use chrono_tz::{OffsetName, Tz};
 use clap::{crate_version, Arg, ArgAction, Command};
+use iana_time_zone::get_timezone;
 #[cfg(all(unix, not(target_os = "macos"), not(target_os = "redox")))]
 use libc::{clock_settime, timespec, CLOCK_REALTIME};
 use std::fs::File;
@@ -272,8 +274,21 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         for date in dates {
             match date {
                 Ok(date) => {
+                    // TODO - Revisit when chrono 0.5 is released. https://github.com/chronotope/chrono/issues/970
+                    let tz = match std::env::var("TZ") {
+                        // TODO Support other time zones...
+                        Ok(s) if s == "UTC0" => Tz::Etc__UTC,
+                        _ => match get_timezone() {
+                            Ok(tz_str) => tz_str.parse().unwrap(),
+                            Err(_) => Tz::Etc__UTC,
+                        },
+                    };
+                    let offset = tz.offset_from_utc_date(&Utc::now().date_naive());
+                    let tz_abbreviation = offset.abbreviation();
                     // GNU `date` uses `%N` for nano seconds, however crate::chrono uses `%f`
-                    let format_string = &format_string.replace("%N", "%f");
+                    let format_string = &format_string
+                        .replace("%N", "%f")
+                        .replace("%Z", tz_abbreviation);
                     // Refuse to pass this string to chrono as it is crashing in this crate
                     if format_string.contains("%#z") {
                         return Err(USimpleError::new(
@@ -403,7 +418,7 @@ fn make_format_string(settings: &Settings) -> &str {
             Rfc3339Format::Ns => "%F %T.%f%:z",
         },
         Format::Custom(ref fmt) => fmt,
-        Format::Default => "%c",
+        Format::Default => "%a %b %e %X %Z %Y",
     }
 }
 
diff --git a/tests/by-util/test_date.rs b/tests/by-util/test_date.rs
index 553414af8..d0a9c09a2 100644
--- a/tests/by-util/test_date.rs
+++ b/tests/by-util/test_date.rs
@@ -144,11 +144,12 @@ fn test_date_utc() {
 #[test]
 fn test_date_utc_issue_6495() {
     new_ucmd!()
+        .env("TZ", "UTC0")
         .arg("-u")
         .arg("-d")
         .arg("@0")
         .succeeds()
-        .stdout_is("Thu Jan  1 00:00:00 1970\n");
+        .stdout_is("Thu Jan  1 00:00:00 UTC 1970\n");
 }
 
 #[test]
@@ -423,16 +424,18 @@ fn test_invalid_date_string() {
 #[test]
 fn test_date_one_digit_date() {
     new_ucmd!()
+        .env("TZ", "UTC0")
         .arg("-d")
         .arg("2000-1-1")
         .succeeds()
-        .stdout_contains("Sat Jan  1 00:00:00 2000");
+        .stdout_only("Sat Jan  1 00:00:00 UTC 2000\n");
 
     new_ucmd!()
+        .env("TZ", "UTC0")
         .arg("-d")
         .arg("2000-1-4")
         .succeeds()
-        .stdout_contains("Tue Jan  4 00:00:00 2000");
+        .stdout_only("Tue Jan  4 00:00:00 UTC 2000\n");
 }
 
 #[test]
@@ -464,6 +467,7 @@ fn test_date_parse_from_format() {
 #[test]
 fn test_date_from_stdin() {
     new_ucmd!()
+        .env("TZ", "UTC0")
         .arg("-f")
         .arg("-")
         .pipe_in(
@@ -473,8 +477,8 @@ fn test_date_from_stdin() {
         )
         .succeeds()
         .stdout_is(
-            "Mon Mar 27 08:30:00 2023\n\
-             Sat Apr  1 12:00:00 2023\n\
-             Sat Apr 15 18:30:00 2023\n",
+            "Mon Mar 27 08:30:00 UTC 2023\n\
+             Sat Apr  1 12:00:00 UTC 2023\n\
+             Sat Apr 15 18:30:00 UTC 2023\n",
         );
 }