timestamps in AR

create_users.rb

class CreateUsers < ActiveRecord::Migration
  def change
    create_table :users do |t|
     ...

      t.datetime 'inserted_at', null: false
      t.datetime 'updated_at', null: false
    end
  end
end

user.rb

class User < ActiveRecord::Base
  private

  def timestamp_attributes_for_create
    [:inserted_at]
  end
end