Fix hoursInDay division constant (#395)

Closes #394.

The constant was incorrect. This also adds a test for a basic
`hour_in_day_with_provider` call.

Author: nekevss

src/builtins/core/zoneddatetime.rs

@@ -761,7 +761,7 @@ impl ZonedDateTime {
         // NOTE: The below should be safe as today_ns and tomorrow_ns should be at most 25 hours.
         // TODO: Tests for the below cast.
         // 10. Return 𝔽(TotalTimeDuration(diff, hour)).
-        Ok(diff.divide(60_000_000_000) as u8)
+        Ok(diff.divide(3_600_000_000_000) as u8)
     }
 }
 
@@ -1643,6 +1643,21 @@ mod tests {
         assert!(result.is_ok());
     }
 
+    #[test]
+    fn zdt_hours_in_day() {
+        let provider = &FsTzdbProvider::default();
+        let zdt_str = "2025-07-04T12:00[UTC][u-ca=iso8601]";
+        let result = ZonedDateTime::from_str_with_provider(
+            zdt_str,
+            Disambiguation::Compatible,
+            OffsetDisambiguation::Reject,
+            provider,
+        )
+        .unwrap();
+
+        assert_eq!(result.hours_in_day_with_provider(provider).unwrap(), 24)
+    }
+
     #[test]
     // https://github.com/tc39/test262/blob/d9b10790bc4bb5b3e1aa895f11cbd2d31a5ec743/test/intl402/Temporal/ZonedDateTime/from/dst-skipped-cross-midnight.js
     fn dst_skipped_cross_midnight() {