Adding jquery-ui datepicker to rails view with Alternate Field and format

jquery-ui-datepicker-rails-part2.html.haml

# in your view (HAML + simple_form, simplified for easier reading)
= simple_form_for @bp_reading do |f|
  = f.input :recorded_at, :as => :string, :input_html => { :class => 'jquery-ui-date'}
  = f.input :recorded_at, :as => :hidden, :input_html => { :id => 'recorded-at-alt'}
  = f.button :submit, :disable_with => "Saving...", :value => "Save"

# in your javascript (coffeescript)
$ ->
  $(".jquery-ui-date").datepicker(
    altField: "#recorded-at-alt",
    altFormat: "yy-mm-d"
  )