diff --git a/proselint/DateCase.yml b/proselint/DateCase.yml
index cdc9685..9aa1bd9 100644
--- a/proselint/DateCase.yml
+++ b/proselint/DateCase.yml
@@ -1,6 +1,6 @@
 extends: existence
 message: With lowercase letters, the periods are standard.
-ignorecase: true
+ignorecase: false
 level: error
 nonword: true
 tokens: