fix birthday_tag

Author: huacnlee

app/helpers/application_helper.rb

@@ -126,7 +126,7 @@ def insert_code_menu_items_tag
 
   def birthday_tag
     if Time.now.month == 10 && Time.now.day == 28
-      age = Time.now.year - 2011 + 1
+      age = Time.now.year - 2011
       title = "Ruby China 创立 #{age} 周年纪念日"
       html = []
       html << "<div style='text-align:center;margin-bottom:20px; line-height:200%;'>"