Fix datetime validation and test timestamp format

- Add proper datetime validation in API with 400 error responses
- Fix test timestamp format (was creating invalid +00:00Z format)
- Time filters now properly validate and return errors on invalid input
- All 26 tests passing with correct filtering behavior

apps/epg/api_views.py

@@ -800,36 +800,56 @@ class ProgramSearchAPIView(APIView):
             desc_whole_words = params.get('description_whole_words', '').lower() in ('true', '1', 'yes')
             filters &= _parse_text_query('description', description, use_regex=desc_regex, whole_words=desc_whole_words)
 
-        # Time filters
+        # Time filters with validation
         start_after = params.get('start_after')
         if start_after:
             dt = parse_datetime(start_after)
-            if dt:
-                filters &= Q(start_time__gte=dt)
+            if dt is None:
+                return Response(
+                    {"error": f"Invalid datetime format for start_after: {start_after}. Use ISO 8601 format (e.g., 2026-02-14T18:00:00Z)"},
+                    status=status.HTTP_400_BAD_REQUEST
+                )
+            filters &= Q(start_time__gte=dt)
 
         start_before = params.get('start_before')
         if start_before:
             dt = parse_datetime(start_before)
-            if dt:
-                filters &= Q(start_time__lte=dt)
+            if dt is None:
+                return Response(
+                    {"error": f"Invalid datetime format for start_before: {start_before}. Use ISO 8601 format."},
+                    status=status.HTTP_400_BAD_REQUEST
+                )
+            filters &= Q(start_time__lte=dt)
 
         end_after = params.get('end_after')
         if end_after:
             dt = parse_datetime(end_after)
-            if dt:
-                filters &= Q(end_time__gte=dt)
+            if dt is None:
+                return Response(
+                    {"error": f"Invalid datetime format for end_after: {end_after}. Use ISO 8601 format."},
+                    status=status.HTTP_400_BAD_REQUEST
+                )
+            filters &= Q(end_time__gte=dt)
 
         end_before = params.get('end_before')
         if end_before:
             dt = parse_datetime(end_before)
-            if dt:
-                filters &= Q(end_time__lte=dt)
+            if dt is None:
+                return Response(
+                    {"error": f"Invalid datetime format for end_before: {end_before}. Use ISO 8601 format."},
+                    status=status.HTTP_400_BAD_REQUEST
+                )
+            filters &= Q(end_time__lte=dt)
 
         airing_at = params.get('airing_at')
         if airing_at:
             dt = parse_datetime(airing_at)
-            if dt:
-                filters &= Q(start_time__lte=dt, end_time__gt=dt)
+            if dt is None:
+                return Response(
+                    {"error": f"Invalid datetime format for airing_at: {airing_at}. Use ISO 8601 format."},
+                    status=status.HTTP_400_BAD_REQUEST
+                )
+            filters &= Q(start_time__lte=dt, end_time__gt=dt)
 
         # Channel/stream filters
         channel = params.get('channel')

tests/test_epg_search_api.py

@@ -244,8 +244,10 @@ class TestEPGSearchAPI:
         dt = datetime.fromisoformat(test_timestamp.replace("Z", "+00:00"))
         
         # Create time window: +/- 2 hours
-        start_after = (dt - timedelta(hours=2)).isoformat() + "Z"
-        start_before = (dt + timedelta(hours=2)).isoformat() + "Z"
+        start_after_dt = dt - timedelta(hours=2)
+        start_before_dt = dt + timedelta(hours=2)
+        start_after = start_after_dt.isoformat().replace("+00:00", "Z")
+        start_before = start_before_dt.isoformat().replace("+00:00", "Z")
         
         result = api_client.search_programs({
             "start_after": start_after,
@@ -254,12 +256,16 @@ class TestEPGSearchAPI:
         })
         
         assert "results" in result
+        assert isinstance(result["results"], list)
         
-        # Verify programs are within range
+        # Verify all returned programs are within the requested range
+        # If no programs exist in this range, results should be empty (count=0)
         for program in result["results"]:
-            start = program["start_time"]
-            assert start >= start_after
-            assert start <= start_before
+            # Parse timestamp for comparison
+            start_dt = datetime.fromisoformat(program["start_time"].replace("Z", "+00:00"))
+            # Programs must be within the filtered range
+            assert start_dt >= start_after_dt, f"Program starts at {start_dt}, before filter start {start_after_dt}"
+            assert start_dt <= start_before_dt, f"Program starts at {start_dt}, after filter end {start_before_dt}"
     
     def test_channel_filter(self, api_client):
         """Test channel name filter"""