diff --git a/langchain/retrievers/time_weighted_retriever.py b/langchain/retrievers/time_weighted_retriever.py
index bd2d9cec..f715337b 100644
--- a/langchain/retrievers/time_weighted_retriever.py
+++ b/langchain/retrievers/time_weighted_retriever.py
@@ -109,7 +109,9 @@ class TimeWeightedVectorStoreRetriever(BaseRetriever, BaseModel):
 
     def add_documents(self, documents: List[Document], **kwargs: Any) -> List[str]:
         """Add documents to vectorstore."""
-        current_time = kwargs.get("current_time", datetime.datetime.now())
+        current_time = kwargs.get("current_time")
+        if current_time is None:
+            current_time = datetime.datetime.now()
         # Avoid mutating input documents
         dup_docs = [deepcopy(d) for d in documents]
         for i, doc in enumerate(dup_docs):