weekday: ignore the weekday when an explicit date is given

src/items/builder.rs

@@ -212,10 +212,15 @@ impl DateTimeBuilder {
     ///     from the base instant.
     ///   - b. Apply time. If time carries an explicit numeric offset, apply the
     ///     offset before setting time.
-    ///   - c. Apply weekday (e.g., "next Friday" or "last Monday").
+    ///   - c. Apply weekday (e.g., "next Friday" or "last Monday"). A weekday
+    ///     is ignored when an explicit calendar date is given.
     ///   - d. Apply fixed offset if present (anchors the instant).
     ///   - e. Apply relative adjustments (e.g., "+3 days", "-2 months").
-    pub(super) fn build(self) -> Result<ParsedDateTime, error::Error> {
+    pub(super) fn build(mut self) -> Result<ParsedDateTime, error::Error> {
+        if self.date.is_some() {
+            self.weekday = None;
+        }
+
         if let Some(date) = self.date.as_ref() {
             if date.year.unwrap_or(0) > 9999 {
                 return self.build_extended();
@@ -902,7 +907,7 @@ mod tests {
     }
 
     #[test]
-    fn build_extended_applies_relative_units_and_weekday() {
+    fn build_extended_applies_relative_units_and_ignores_weekday_with_date() {
         let base = "2000-01-01 00:00:00"
             .parse::<DateTime>()
             .unwrap()
@@ -918,7 +923,9 @@ mod tests {
         ])
         .unwrap();
         let dt = expect_extended_datetime(builder.set_base(base).build().unwrap());
-        assert_eq!((dt.year, dt.month, dt.day), (10000, 1, 4));
+        // The weekday is ignored because a date is given, so only the relative
+        // items move it (GNU: `next mon 10000-01-01 +1 day` is 10000-01-02).
+        assert_eq!((dt.year, dt.month, dt.day), (10000, 1, 2));
         assert_eq!((dt.hour, dt.minute, dt.second), (2, 3, 4));
     }
 

tests/date.rs

@@ -434,3 +434,48 @@ fn test_zone_item_keeps_time_of_day_with_relative(#[case] input: &str, #[case] e
         "`{input}` should resolve to {expected} in its own zone"
     );
 }
+
+// A weekday is ignored when an explicit date is given, as in GNU date
+// (checked against coreutils 9.12, base Thursday 2026-10-01).
+#[rstest]
+#[case::mismatching_named_month("Wednesday August 17 2026", "2026-08-17 00:00:00")]
+#[case::matching_named_month("Monday August 17 2026", "2026-08-17 00:00:00")]
+#[case::abbreviated_with_comma("Wed, Aug 17 2026", "2026-08-17 00:00:00")]
+#[case::day_month_with_comma("Wednesday, 17 August 2026", "2026-08-17 00:00:00")]
+#[case::named_month_without_year("Wed Aug 17", "2026-08-17 00:00:00")]
+#[case::iso_date("Wed 2026-08-17", "2026-08-17 00:00:00")]
+#[case::iso_date_then_weekday("2026-08-17 Wed", "2026-08-17 00:00:00")]
+#[case::us_date("Wed 08/17/2026", "2026-08-17 00:00:00")]
+#[case::date_and_time("Wed 2026-08-17 10:30", "2026-08-17 10:30:00")]
+#[case::time_before_date("Wed 10:30 2026-08-17", "2026-08-17 10:30:00")]
+#[case::iso_datetime("2026-08-17T10:30:00 Wed", "2026-08-17 10:30:00")]
+#[case::next_weekday("next Friday Sep 25 2026", "2026-09-25 00:00:00")]
+#[case::next_other_weekday("next Sunday Sep 25 2026", "2026-09-25 00:00:00")]
+#[case::last_weekday("last Wed 2026-08-17", "2026-08-17 00:00:00")]
+#[case::ordinal_weekday("third Wed 2026-08-17", "2026-08-17 00:00:00")]
+#[case::numeric_ordinal_weekday("2 Wed 2026-08-17", "2026-08-17 00:00:00")]
+#[case::date_output_format("Sun Sep 25 12:00:00 AM UTC 2026", "2026-09-25 00:00:00")]
+// Relative items still apply on top of the given date.
+#[case::relative_day("Wed 2026-08-17 +1 day", "2026-08-18 00:00:00")]
+#[case::relative_week("Wed 2026-08-17 next week", "2026-08-24 00:00:00")]
+// Without a date, the weekday is still honoured.
+#[case::weekday_alone("Wed", "2026-10-07 00:00:00")]
+#[case::weekday_and_time("Wed 10:30", "2026-10-07 10:30:00")]
+#[case::weekday_and_relative("Wed +1 day", "2026-10-08 00:00:00")]
+fn test_weekday_ignored_with_explicit_date(#[case] input: &str, #[case] expected: &str) {
+    let base = "2026-10-01 12:00:00"
+        .parse::<DateTime>()
+        .unwrap()
+        .to_zoned(TimeZone::UTC)
+        .unwrap();
+
+    let parsed = parse_datetime::parse_datetime_at_date(base, input)
+        .unwrap()
+        .expect_in_range();
+
+    assert_eq!(
+        parsed.datetime().to_string(),
+        expected.parse::<DateTime>().unwrap().to_string(),
+        "`{input}` should resolve to {expected}"
+    );
+}