diff --git a/lib/validates_timeliness/formats.rb b/lib/validates_timeliness/formats.rb
index dc254c2..c6b9fd5 100644
--- a/lib/validates_timeliness/formats.rb
+++ b/lib/validates_timeliness/formats.rb
@@ -96,6 +96,7 @@ module ValidatesTimeliness
     @@datetime_formats = [
       'yyyy-mm-dd hh:nn:ss',
       'yyyy-mm-dd h:nn',
+      'yyyy-mm-dd h:nn_ampm',
       'yyyy-mm-dd hh:nn:ss.u',
       'm/d/yy h:nn:ss',
       'm/d/yy h:nn_ampm',