diff --git a/activesupport/lib/active_support/time_with_zone.rb b/activesupport/lib/active_support/time_with_zone.rb
index 0dbc198ea2891..89f37114fd7aa 100644
--- a/activesupport/lib/active_support/time_with_zone.rb
+++ b/activesupport/lib/active_support/time_with_zone.rb
@@ -80,6 +80,12 @@ def localtime
     end
     alias_method :getlocal, :localtime
 
+    # Returns true if the the current time is within Daylight Savings Time for the
+    # specified time zone.
+    #
+    #    Time.zone = 'Eastern Time (US & Canada)'    # => 'Eastern Time (US & Canada)'
+    #    Time.zone.parse("2012-5-30").dst?           # => true
+    #    Time.zone.parse("2012-11-30").dst?          # => false
     def dst?
       period.dst?
     end