date: parse <digits>j as a local time of day

src/uu/date/src/date.rs

@@ -418,8 +418,14 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
             // - Semantics: a pure decimal number denotes today's time-of-day (HH or HHMM).
             //   Examples: "0"/"00" => 00:00 today; "7"/"07" => 07:00 today; "0700" => 07:00 today.
             // For all other forms, fall back to the general parser.
-            let is_pure_digits =
-                !input.is_empty() && input.len() <= 4 && input.chars().all(|c| c.is_ascii_digit());
+            //
+            // GNU compatibility (Military timezone 'J' after a time):
+            // 'J' is local time, so "<digits>j"/"<digits>J" is the same time-of-day form
+            // as the bare "<digits>" input ("9j" == "9"). Strip it before the digit check.
+            let time_digits = input.strip_suffix(['j', 'J']).unwrap_or(input);
+            let is_pure_digits = !time_digits.is_empty()
+                && time_digits.len() <= 4
+                && time_digits.chars().all(|c| c.is_ascii_digit());
 
             let date = if is_empty_or_whitespace || is_military_j {
                 // Treat empty string or 'J' as midnight today (00:00:00) in local time
@@ -463,11 +469,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
                 let composed = format!("{date_part} {total_hours:02}:00:00 +00:00");
                 parse_date(composed, &now, DebugOptions::new(settings.debug, false))
             } else if is_pure_digits {
-                // Derive HH and MM from the input
-                let (hh_opt, mm_opt) = if input.len() <= 2 {
-                    (input.parse::<u32>().ok(), Some(0u32))
+                // Derive HH and MM from the digits
+                let (hh_opt, mm_opt) = if time_digits.len() <= 2 {
+                    (time_digits.parse::<u32>().ok(), Some(0u32))
                 } else {
-                    let (h, m) = input.split_at(input.len() - 2);
+                    let (h, m) = time_digits.split_at(time_digits.len() - 2);
                     (h.parse::<u32>().ok(), m.parse::<u32>().ok())
                 };
 

tests/by-util/test_date.rs

@@ -1263,6 +1263,41 @@ fn test_date_military_timezone_j_variations() {
         .stdout_contains("UTC");
 }
 
+#[test]
+fn test_date_military_timezone_j_with_time() {
+    // 'J' is local time, so "<digits>j" is the time-of-day form (HH or HHMM)
+    // in the local zone, same as the bare "<digits>" input. GNU accepts it.
+    let test_cases = vec![
+        ("8j", "08:00:00"),
+        ("9j", "09:00:00"),
+        ("9J", "09:00:00"),
+        ("12j", "12:00:00"),
+        ("1230j", "12:30:00"),
+        ("0j", "00:00:00"),
+        ("00j", "00:00:00"),
+    ];
+
+    for (input, expected) in test_cases {
+        new_ucmd!()
+            .env("TZ", "UTC")
+            .arg("-d")
+            .arg(input)
+            .arg("+%T")
+            .succeeds()
+            .stdout_is(format!("{expected}\n"));
+    }
+
+    // Out-of-range times are rejected, same as the bare digit form
+    for input in ["2400j", "2360j", "12345j"] {
+        new_ucmd!()
+            .env("TZ", "UTC")
+            .arg("-d")
+            .arg(input)
+            .fails()
+            .stderr_contains("invalid date");
+    }
+}
+
 #[test]
 fn test_date_empty_string() {
     // Empty string should be treated as midnight today
@@ -1973,20 +2008,19 @@ fn test_date_bare_timezone_abbreviation() {
 }
 
 #[test]
-#[ignore = "https://github.com/uutils/parse_datetime/issues/279 — GNU date silently ignores unrecognized trailing tokens (e.g. `8j`), but parse_datetime rejects them."]
+#[ignore = "https://github.com/uutils/parse_datetime/issues/279. GNU date silently ignores unrecognized trailing tokens (e.g. `8 j`), but parse_datetime rejects them."]
 fn test_date_ignores_unrecognized_trailing_tokens() {
     // GNU compatibility: trailing unknown word-tokens after a valid number are ignored.
-    // GNU parses `8j`, `8 j`, etc. as hour 8; our parse_datetime crate errors out.
-    for input in ["8j", "8 j"] {
-        new_ucmd!()
-            .env("TZ", "UTC")
-            .arg("-u")
-            .arg("-d")
-            .arg(input)
-            .arg("+%H:%M:%S")
-            .succeeds()
-            .stdout_only("08:00:00\n");
-    }
+    // GNU parses `8 j` (number, space, token) as hour 8; our parse_datetime crate errors out.
+    // The no-space `8j` form is handled directly (see test_date_military_timezone_j_with_time).
+    new_ucmd!()
+        .env("TZ", "UTC")
+        .arg("-u")
+        .arg("-d")
+        .arg("8 j")
+        .arg("+%H:%M:%S")
+        .succeeds()
+        .stdout_only("08:00:00\n");
 }
 
 #[test]