diff --git a/app/models/bulletin.rb b/app/models/bulletin.rb
index 601146a..8bfd6ac 100644
--- a/app/models/bulletin.rb
+++ b/app/models/bulletin.rb
@@ -20,6 +20,7 @@ class Bulletin
   field :rss2_sn
   field :approved, :type => Boolean, :default => false
   field :is_preview, :type => Boolean, :default => false
+  field :expirable_created_at, type: DateTime
 
   field :email_id
   field :email_sent, :type => Boolean, :default => false
@@ -41,6 +42,12 @@ class Bulletin
   scope :can_display, ->{where(:is_hidden=>false).any_of({:postdate.lt=>Time.now, :deadline.gt=>Time.now},{:postdate.lt=>Time.now, :deadline=>nil}).order_by([:is_top, :desc])}
   scope :is_approved, ->{where(:approved => true)}
 
+  before_create :set_expire
+  def set_expire
+    self.expirable_created_at = Time.now if self.is_preview
+    return true
+  end
+
   def update_user
     User.find(update_user_id) rescue nil
   end
diff --git a/app/views/admin/announcements/_form.html.erb b/app/views/admin/announcements/_form.html.erb
index 0f64704..38ead79 100644
--- a/app/views/admin/announcements/_form.html.erb
+++ b/app/views/admin/announcements/_form.html.erb
@@ -23,7 +23,6 @@
     <li><a href="#imageupload" data-toggle="tab"><%= t(:image) %></a></li>
     <li><a href="#mail-group" data-toggle="tab"><%= t('announcement.email_reminder')%></a></li>    
   </ul>
-
   <!-- Module -->
   <div class="tab-content module-area">
 
@@ -42,14 +41,14 @@
       <div class="control-group">
         <label class="control-label muted"><%= t(:start_date) %></label>
         <div class="controls">
-          <%= f.datetime_picker :postdate, :no_label => true %>
+          <%= f.datetime_picker :postdate, :no_label => true, :new_record => @bulletin.new_record? %>
         </div>
       </div>
 
       <div class="control-group">
         <label class="control-label muted"><%= t(:end_date) %></label>
         <div class="controls">
-          <%= f.datetime_picker :deadline, :no_label => true %>
+          <%= f.datetime_picker :deadline, :no_label => true, :new_record => @bulletin.new_record?  %>
         </div>
       </div>
 
@@ -389,10 +388,10 @@
           });
 
           var slug = data.split('/')[(data.split('/').length-1)];
-          $('#preview-iframe').on('load', function(){
-            $.get('/admin/announcement/destroy_preview/'+slug,function(data){
-            });
-          });
+          // $('#preview-iframe').on('load', function(){
+          //   $.get('/admin/announcement/destroy_preview/'+slug,function(data){
+          //   });
+          // });
         });
         $('.main-forms input[name="_method"]').val(method);
         return false;
diff --git a/lib/announcement/engine.rb b/lib/announcement/engine.rb
index 174c9ad..9c52373 100644
--- a/lib/announcement/engine.rb
+++ b/lib/announcement/engine.rb
@@ -1,3 +1,4 @@
+require "yaml"
 module Announcement
   class Engine < ::Rails::Engine
     initializer "announcement" do 
@@ -45,6 +46,11 @@ module Announcement
         end
 
       end
+      temp = YAML.load_file(File.join(Rails.root,"config","mongoid.yml"))
+      dbsettings = temp["production"]["sessions"]["default"]
+      s = Moped::Session.new(dbsettings["hosts"])
+      s.use dbsettings["database"] 
+      s[:bulletins].indexes.create({expirable_created_at: 1},{ expireAfterSeconds: 180 })
     end
   end
 end
\ No newline at end of file