<%= date_select(:customer, :birthday) %>
As far as I understand it Rails is expecting :customer to be an
ActiveRecord subclass and :birthday to be an attribute of Customer.
When using params[:customer] in your controller for "mass assignment"
it will take care of setting my_customer.birthday automatically for
Sorry, I don't know if Rails supplies a convenient way to parse this
into a Date object individually. But, it likely has something for