date: fix %Z specifier does not print TZ abbr

Cargo.toml

@@ -268,6 +268,8 @@ chrono = { version = "^0.4.31", default-features = false, features = [
   "alloc",
   "clock",
 ] }
+chrono-tz = "0.8.3"
+iana-time-zone = "0.1.57"
 clap = { version = "4.4", features = ["wrap_help", "cargo"] }
 clap_complete = "4.4"
 clap_mangen = "0.2"

src/uu/date/Cargo.toml

@@ -20,6 +20,8 @@ chrono = { workspace = true }
 clap = { workspace = true }
 uucore = { workspace = true }
 parse_datetime = { workspace = true }
+chrono-tz = { workspace = true }
+iana-time-zone = { workspace = true }
 
 [target.'cfg(unix)'.dependencies]
 libc = { workspace = true }

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, Duration, FixedOffset, Local, Offset, Utc};
+use chrono::{DateTime, Duration, FixedOffset, Local, Offset, 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;
@@ -265,8 +267,15 @@ 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_str = get_timezone().unwrap_or("Etc/UTC".to_string());
+                    let tz: Tz = tz_str.parse().unwrap();
+                    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(
@@ -396,7 +405,7 @@ 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 %-d %X %Z %Y",
     }
 }