Ruby datetime属性值未保存在SQLite DB中

我正在尝试将具有'sale_price'（浮动）和'order_date'（日期时间）属性的Order对象保存到SQLite数据库。日志中的所有内容看起来都好像为每个Order对象正确保存了两种属性类型。但是，当我检查数据库时，所有Order对象的'order_date'属性均为nil。这是代码：

response["orders"].each do |n|

        balance = n["balance"]

        sale_price = balance.to_f

        order_date = n["created_date"]

        order = Order.new(sale_price: sale_price, order_date: order_date)

        if Order.where(order_date: order_date).exists?

            puts "That order already exists in the DB"

        else

            if (order.sale_price || order.order_date) != nil 

                order.save

            else
                p "The sale price is nil"
            end

        end     

    end

这是日志中的示例事务外观：

    Order Exists (0.9ms)  SELECT 1 AS one FROM "orders" WHERE "orders"."order_date" = '2013-12-06T15:53:36.424Z' LIMIT 1
   (0.1ms)  begin transaction
  SQL (0.5ms)  INSERT INTO "orders" ("created_at", "order_date", "sale_price", "updated_at") VALUES (?, ?, ?, ?)  [["created_at", Tue, 27 May 2014 22:59:02 UTC +00:00], ["order_date", Fri, 06 Dec 2013 15:53:36 UTC +00:00], ["sale_price", 20548.0], ["updated_at", Tue, 27 May 2014 22:59:02 UTC +00:00]]
   (3.1ms)  commit transaction

有什么想法吗？