How to update Activerecord with unixtimestamp time?

Question

Ruby on Rails

I suspect that the solution is simple, but I did not find something in the dock.
With the help of ajax, I send a parameter update, where one of the attributes is unixtimestamp.
But in Order and in the database it is datetime.
Now I do this:

order = params[:order]
order[:order_date] = Time.at(order[:order_date].to_i).to_datetime
order_item.update_attributes(order.permit( :order_date))

But I suspect this is a very crooked decision and everything has already been done before me.