diff --git a/db/migrate/20150619060110_homework_common_time.rb b/db/migrate/20150619060110_homework_common_time.rb
new file mode 100644
index 000000000..c574ad93c
--- /dev/null
+++ b/db/migrate/20150619060110_homework_common_time.rb
@@ -0,0 +1,19 @@
+class HomeworkCommonTime < ActiveRecord::Migration
+  def up
+    count = StudentWork.all.count / 100 + 1
+    transaction do
+      for i in 1 ... count do i
+      StudentWork.page(i).per(100).each do |homework|
+        old_homework = HomeworkAttach.where(:user_id => homework.user_id, :name => homework.name, :description => homework.description).first
+        if old_homework
+          homework.update_column('created_at', old_homework.created_at)
+        end
+      end
+      end
+      puts i.to_s
+    end
+  end
+
+  def down
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 68f00c1cd..420432355 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 20150604153000) do
+ActiveRecord::Schema.define(:version => 20150619060110) do
 
   create_table "activities", :force => true do |t|
     t.integer "act_id",   :null => false