diff --git a/core/config.py b/core/config.py
index e644601..98d61c8 100644
--- a/core/config.py
+++ b/core/config.py
@@ -261,7 +261,7 @@ class Settings(BaseSettings):
         "PT1H": "H",
         "P1D": "D",
         "P1W": "W",
-        "P1M": "M",
+        "P1M": "MS",
     }
 
     TIME_GRAIN_EXPRESSIONS = {