diff --git a/TODO b/TODO
index dbf9c89..c85ebe7 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,4 @@
 - :format option
 - :with_date and :with_time options
 - valid formats could come from locale file
-- formats to use month and day names from i18n
 - add replace_formats instead add_formats :before
diff --git a/lib/validates_timeliness/formats.rb b/lib/validates_timeliness/formats.rb
index e419fd9..ba242b7 100644
--- a/lib/validates_timeliness/formats.rb
+++ b/lib/validates_timeliness/formats.rb
@@ -1,3 +1,5 @@
+require 'date'
+
 module ValidatesTimeliness
   
   # A date and time format regular expression generator. Allows you to 
@@ -297,9 +299,17 @@ module ValidatesTimeliness
       
       def month_index(month)
         return month.to_i if month.to_i.nonzero?
-        Date::ABBR_MONTHNAMES.index(month.capitalize) || Date::MONTHNAMES.index(month.capitalize)
+        abbr_month_names.index(month.capitalize) || month_names.index(month.capitalize)
       end
-    
+
+      def month_names
+        defined?(I18n) ? I18n.t('date.month_names') : Date::MONTHNAMES
+      end
+
+      def abbr_month_names
+        defined?(I18n) ? I18n.t('date.abbr_month_names') : Date::ABBR_MONTHNAMES
+      end
+
       def microseconds(usec)
         (".#{usec}".to_f * 1_000_000).to_i
       end