gistfile1.rb

##formtastic_datepicker_interface
module Formtastic
  module DatePicker
    protected

    def datepicker_input(method, options = {})
      format = options[:format] || ActiveSupport::CoreExtensions::Date::Conversions::DATE_FORMATS[:default] || '%d %b %Y'
      string_input(method, datepicker_options(format, object.send(method)).merge(options))
    end

    # Generate html input options for the datepicker_input
    #
    def datepicker_options(format, value = nil)
      datepicker_options = {:value => value.try(:strftime, format), :input_html => {:class => 'ui-datepicker'}}
    end
  end
end

##config/environment.rb
  config.after_initialize do
    require 'user_last_activity_updater'
    Formtastic::SemanticFormBuilder.send(:include, Formtastic::DatePicker)
  end

##application.js
$(document).ready(function(){
  $('input.ui-datepicker').datepicker();
});


#usage in view file
    = f.input :reminder_date, :as => :datepicker