fix(explore): fix issue with not being able to save explore queries with a start and end time stamp selected

src/sentry/explore/endpoints/serializers.py

@@ -204,7 +204,10 @@ def validate(self, data):
 
         for key in query_keys:
             if data.get(key) is not None:
-                query[key] = data[key]
+                value = data[key]
+                if key in ("start", "end"):
+                    value = value.isoformat()
+                query[key] = value
 
         if "query" in data:
             query["query"] = []

tests/sentry/explore/endpoints/test_explore_saved_queries.py

@@ -1270,3 +1270,20 @@ def test_post_metrics_dataset_requires_metric_field(self) -> None:
             )
         assert response.status_code == 400, response.content
         assert "Metric field is required for metrics dataset" in str(response.data)
+
+    def test_save_with_start_and_end_time(self) -> None:
+        with self.feature(self.features):
+            response = self.client.post(
+                self.url,
+                {
+                    "name": "Start and end time query",
+                    "projects": self.project_ids,
+                    "dataset": "spans",
+                    "start": "2025-11-12T23:00:00.000Z",
+                    "end": "2025-11-20T22:59:59.000Z",
+                },
+            )
+        assert response.status_code == 201, response.content
+        data = response.data
+        assert data["start"] is not None
+        assert data["end"] is not None