diff --git a/lightrag/kg/chroma_impl.py b/lightrag/kg/chroma_impl.py
index 627cf480..c7f8c47e 100644
--- a/lightrag/kg/chroma_impl.py
+++ b/lightrag/kg/chroma_impl.py
@@ -114,11 +114,17 @@ class ChromaVectorDBStorage(BaseVectorStorage):
             return
 
         try:
+            import time
+            current_time = int(time.time())
+            
             ids = list(data.keys())
             documents = [v["content"] for v in data.values()]
             metadatas = [
-                {k: v for k, v in item.items() if k in self.meta_fields}
-                or {"_default": "true"}
+                {
+                    **{k: v for k, v in item.items() if k in self.meta_fields},
+                    "created_at": current_time,
+                }
+                or {"_default": "true", "created_at": current_time}
                 for item in data.values()
             ]
 
@@ -183,6 +189,7 @@ class ChromaVectorDBStorage(BaseVectorStorage):
                     "id": results["ids"][0][i],
                     "distance": 1 - results["distances"][0][i],
                     "content": results["documents"][0][i],
+                    "created_at": results["metadatas"][0][i].get("created_at"),
                     **results["metadatas"][0][i],
                 }
                 for i in range(len(results["ids"][0]))
@@ -298,6 +305,7 @@ class ChromaVectorDBStorage(BaseVectorStorage):
                 "id": result["ids"][0],
                 "vector": result["embeddings"][0],
                 "content": result["documents"][0],
+                "created_at": result["metadatas"][0].get("created_at"),
                 **result["metadatas"][0],
             }
         except Exception as e:
@@ -331,6 +339,7 @@ class ChromaVectorDBStorage(BaseVectorStorage):
                     "id": result["ids"][i],
                     "vector": result["embeddings"][i],
                     "content": result["documents"][i],
+                    "created_at": result["metadatas"][i].get("created_at"),
                     **result["metadatas"][i],
                 }
                 for i in range(len(result["ids"]))