diff --git a/src/cache_manager.py b/src/cache_manager.py
index 65c392e7..9f7de8ea 100644
--- a/src/cache_manager.py
+++ b/src/cache_manager.py
@@ -107,7 +107,7 @@ class CacheManager:
 
                 # Then save to disk
                 with open(cache_path, 'w') as f:
-                    json.dump(data, f)
+                    json.dump(data, f, cls=DateTimeEncoder)
         except Exception as e:
             self.logger.error(f"Error saving cache for {key}: {e}")