diff --git a/jupyter_client/jsonutil.py b/jupyter_client/jsonutil.py
index 2ba640fe..1d001cb5 100644
--- a/jupyter_client/jsonutil.py
+++ b/jupyter_client/jsonutil.py
@@ -28,7 +28,7 @@
 
 # holy crap, strptime is not threadsafe.
 # Calling it once at import seems to help.
-datetime.strptime("1", "%d")  # noqa
+datetime.strptime("2000-01-01", "%Y-%m-%d")  # noqa
 
 # -----------------------------------------------------------------------------
 # Classes and functions