date: add regression test for military time parsing tz correctly

Author: cerdelen

tests/by-util/test_date.rs

@@ -1132,6 +1132,52 @@ fn test_date_military_timezone_with_offset_variations() {
     }
 }
 
+#[test]
+fn test_date_military_timezone_with_offset_and_date() {
+    use chrono::{Duration, Utc};
+
+    let today = Utc::now().date_naive();
+
+    let test_cases = vec![
+        ("m", -1), // M = UTC+12
+        ("a", -1), // A = UTC+1
+        ("n",  0), // N = UTC-1
+        ("y",  0), // N = UTC-12
+        ("z",  0), // Z = UTC
+
+        // same day hour offsets
+        ("n2", 0),
+
+        // midnight crossings with hour offsets back to today
+        ("a1", 0), // exactly to midnight
+        ("a5", 0), // "overflow" midnight
+        ("m23", 0),
+
+        // midnight crossings with hour offsets to tomorrow
+        ("n23", 1),
+        ("y23", 1),
+    ];
+
+    for (input, day_delta) in test_cases {
+        let expected_date = today
+            .checked_add_signed(Duration::days(day_delta))
+            .unwrap();
+
+        let expected = format!(
+            "{}\n",
+            expected_date.format("%F"),
+        );
+
+        new_ucmd!()
+            .env("TZ", "UTC")
+            .arg("-d")
+            .arg(input)
+            .arg("+%F")
+            .succeeds()
+            .stdout_is(expected);
+    }
+}
+
 // Locale-aware hour formatting tests
 #[test]
 #[cfg(unix)]