diff --git a/tagging/update_wiki.py b/tagging/update_wiki.py
index 0277f390..6e1cb36d 100755
--- a/tagging/update_wiki.py
+++ b/tagging/update_wiki.py
@@ -53,7 +53,7 @@ def get_manifest_timestamp(manifest_file: Path) -> str:
 
 
 def get_manifest_month(manifest_file: Path) -> str:
-    return get_manifest_timestamp(manifest_file)[:10]
+    return get_manifest_timestamp(manifest_file)[:7]
 
 
 def remove_old_manifests(wiki_dir: Path) -> None: