diff --git a/shell.nix b/shell.nix
index 5627f92..61cd94a 100644
--- a/shell.nix
+++ b/shell.nix
@@ -7,6 +7,7 @@ pkgs.mkShell {
         numpy
         openpyxl
         pandas
+        python-dateutil
     ]))
   ];
 }