Index: application_helper.rb
===================================================================
--- application_helper.rb	(revision 4761)
+++ application_helper.rb	(working copy)
@@ -166,7 +166,7 @@
   end
   
   def format_activity_day(date)
-    date == Date.today ? l(:label_today).titleize : format_date(date)
+    date == Date.today ? l(:label_today).titleize : (Date.today-date == 1 ? l(:label_yesterday).titleize : format_date(date))
   end
   
   def format_activity_description(text)