documenting monday and sunday methods

railties/guides/source/active_support_core_extensions.textile

@@ -3053,6 +3053,17 @@ d.end_of_week(:sunday)       # => Sat, 08 May 2010
 
 +beginning_of_week+ is aliased to +at_beginning_of_week+ and +end_of_week+ is aliased to +at_end_of_week+.
 
+h6. +monday+, +sunday+
+
+The methods +monday+ and +sunday+ return the dates for the beginning and
+end of the week, respectively. Weeks are assumed to start on Monday.
+
+<ruby>
+d = Date.new(2010, 5, 8)     # => Sat, 08 May 2010
+d.monday                     # => Mon, 03 May 2010
+d.sunday                     # => Sun, 09 May 2010
+</ruby>
+
 h6. +prev_week+, +next_week+
 
 The method +next_week+ receives a symbol with a day name in English (in lowercase, default is +:monday+) and it returns the date corresponding to that day: