Ruby on Rails

I'm using Rails version 3.2 and Ruby 1.9.3

I'm trying to make within a form_tag a datepicker field. In my GemFile I have added gem 'jquery-rails' and gem 'jquery_datepicker'. In the rails console I have used the command: rails generate jquery:install --ui

Application.js looks like this:

// This is a manifest file that'll be compiled into application.js, which will include all the files  // listed below.  //  // Any JavaScript/Coffee file within this directory, lib/assets/javascripts, vendor/assets/javascripts,  // or vendor/assets/javascripts of plugins, if any, can be referenced here using a relative path.  //  // It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the  // the compiled file.  //  // WARNING: THE FIRST BLANK LINE MARKS THE END OF WHAT'S TO BE PROCESSED, ANY BLANK LINE SHOULD  // GO AFTER THE REQUIRES BELOW.  //  //= require jquery  //= require jquery_ujs  //= require jquery_ui  //= require jquery-ui-timepicker-addon.js  //= require_tree .

Application.css:

/*   * This is a manifest file that'll be compiled into application.css, which will include all the files   * listed below.   *   * Any CSS and SCSS file within this directory, lib/assets/stylesheets, vendor/assets/stylesheets,   * or vendor/assets/stylesheets of plugins, if any, can be referenced here using a relative path.   *   * You're free to add application-wide styles to this file and they'll appear at the top of the   * compiled file, but it's generally better to create a new file per style scope.   *   *= require_self   *= require_tree .   *= require_jquery.ui.datepicker  */

And in the view:

<%= form_tag url: {action: 'do_something'} do |f| %>
		<%= text_field_tag :birth_date, '', :class => "datepicker" %>
		<%= submit_tag "Do something man!"%>
		<% end %>

What's the proper calling of datepicker function for form_tag?