class ChangeFormatToDateInActualites < ActiveRecord::Migration
  def up
    remove_column :actualites, :date
    add_column :actualites, :date, :date
  end
  def down
    remove_column :actualites, :date
    add_column :actualites, :date, :string
  end
end

class ChangeFormatToDateInActualites < ActiveRecord::Migration
  def change
    change_column :actualites, :date, :date
  end
end

--- 
+++ 
@@ -1,5 +1,10 @@
 class ChangeFormatToDateInActualites < ActiveRecord::Migration
-  def change
-    change_column :actualites, :date, :date
+  def up
+    remove_column :actualites, :date
+    add_column :actualites, :date, :date
+  end
+  def down
+    remove_column :actualites, :date
+    add_column :actualites, :date, :string
   end
 end
Fix - migration for PG
