Merge pull request #255 from ChrisDryden/fix-tz-prefix-with-base-date

fix: TZ prefix should override base date timezone

src/items/builder.rs

@@ -187,9 +187,13 @@ impl DateTimeBuilder {
     ///   - e. Apply final fixed offset if present.
     pub(super) fn build(self) -> Result<Zoned, error::Error> {
         // 1. Choose the base instant.
-        let base = match (self.base, &self.timezone) {
-            (Some(b), _) => b,
-            (None, Some(tz)) => jiff::Timestamp::now().to_zoned(tz.clone()),
+        // If a TZ="..." prefix was parsed, it should override the base's timezone
+        // while keeping the base's timestamp for relative date calculations.
+        let has_timezone = self.timezone.is_some();
+        let base = match (self.base, self.timezone) {
+            (Some(b), Some(tz)) => b.timestamp().to_zoned(tz),
+            (Some(b), None) => b,
+            (None, Some(tz)) => jiff::Timestamp::now().to_zoned(tz),
             (None, None) => Zoned::now(),
         };
 
@@ -204,7 +208,7 @@ impl DateTimeBuilder {
             || self.time.is_some()
             || self.weekday.is_some()
             || self.offset.is_some()
-            || self.timezone.is_some();
+            || has_timezone;
 
         let mut dt = if need_midnight {
             base.with().time(civil::time(0, 0, 0, 0)).build()?