diff --git a/litellm/proxy/management_endpoints/model_management_endpoints.py b/litellm/proxy/management_endpoints/model_management_endpoints.py
index fc0868a5fc9..609f367e36d 100644
--- a/litellm/proxy/management_endpoints/model_management_endpoints.py
+++ b/litellm/proxy/management_endpoints/model_management_endpoints.py
@@ -1069,6 +1069,12 @@ def _loaded_catalog_entry(
     return loaded_catalog().get(catalog_key, MappingProxyType({}))
 
 
+def _json_temporal_default(value: object) -> str:
+    if isinstance(value, (datetime.datetime, datetime.date, datetime.time)):
+        return value.isoformat()
+    raise TypeError(f"Object of type {type(value).__name__} is not JSON serializable")
+
+
 def update_db_model(
     db_model: Deployment,
     updated_patch: updateDeployment,
@@ -1168,7 +1174,8 @@ def update_db_model(
     prisma_compatible_model_dict: Final = PrismaCompatibleUpdateDBModel(
         model_name=merged_model_name,
         litellm_params=json.dumps(merged_litellm_params),
-        model_info=json.dumps(merged_model_info),
+        # date/time values nest inside model_info (e.g. access_windows start/end)
+        model_info=json.dumps(merged_model_info, default=_json_temporal_default),
     )
 
     if updated_patch.blocked is not None:
diff --git a/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py b/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py
index 303b8e060ed..0dab4f88fa7 100644
--- a/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py
+++ b/tests/unit/proxy/management_endpoints/test_model_management_endpoints.py
@@ -3647,6 +3647,64 @@ class TestUpdateDBModelBlocked:
         assert "blocked" not in result
 
 
+class TestJsonTemporalDefault:
+    def test_raises_type_error_for_unsupported_values(self):
+        from litellm.proxy.management_endpoints.model_management_endpoints import (
+            _json_temporal_default,
+        )
+
+        with pytest.raises(TypeError, match="not JSON serializable"):
+            _json_temporal_default(object())
+
+    def test_isoformats_date_and_time(self):
+        import datetime
+
+        from litellm.proxy.management_endpoints.model_management_endpoints import (
+            _json_temporal_default,
+        )
+
+        assert _json_temporal_default(datetime.time(9, 30)) == "09:30:00"
+        assert _json_temporal_default(datetime.date(2026, 1, 2)) == "2026-01-02"
+
+
+class TestUpdateDBModelAccessWindows:
+    """model_info.access_windows holds datetime.time values; editing a model with a
+    saved window must not 500 on json.dumps (issue #46872)."""
+
+    def test_update_db_model_serializes_access_window_times(self):
+        import datetime
+
+        from litellm.proxy.management_endpoints.model_management_endpoints import update_db_model
+        from litellm.router_utils.access_windows import parse_access_windows
+        from litellm.types.router import Deployment, LiteLLM_Params, ModelInfo, updateDeployment
+
+        db_model = Deployment(
+            model_name="gpt-4o",
+            litellm_params=LiteLLM_Params(model="openai/gpt-4o"),
+            model_info=ModelInfo(
+                id="dep-window",
+                access_windows=(
+                    {
+                        "start": datetime.time(9, 0),
+                        "end": datetime.time(17, 0),
+                        "timezone": "America/New_York",
+                        "team_ids": ("team-1",),
+                    },
+                ),
+            ),
+        )
+
+        result = update_db_model(db_model=db_model, updated_patch=updateDeployment())
+
+        stored = json.loads(result["model_info"])
+        assert stored["access_windows"][0]["start"] == "09:00:00"
+        assert stored["access_windows"][0]["end"] == "17:00:00"
+        # the stored JSON still parses back into valid windows - no data lost
+        windows = parse_access_windows(stored)
+        assert len(windows) == 1
+        assert windows[0].start == datetime.time(9, 0)
+
+
 class TestUpdateDBModelKeepsLegacyDropParams:
     def test_partial_patch_keeps_encrypted_string_drop_params(self, monkeypatch):
         from litellm.proxy.common_utils.encrypt_decrypt_utils import decrypt_value_helper