diff --git a/components/date_picker/theme.css b/components/date_picker/theme.css
index ded09687..bfac22ef 100644
--- a/components/date_picker/theme.css
+++ b/components/date_picker/theme.css
@@ -180,6 +180,7 @@
 
 .month {
   background-color: var(--calendar-primary-contrast-color);
+  width: 100%;
 }
 
 .slideRightEnter,