gistfile1.rb

require 'active_support/concern'

module ActiveModel
  module DatetimeAttributes
    extend ActiveSupport::Concern

    included do
      def self.attr_datetime(datetime_attribute, options = {})
        time_attr = options[:time_attr] || :"#{datetime_attribute}_time"
        date_attr = options[:date_attr] || :"#{datetime_attribute}_date"

        attr_writer date_attr
        attr_writer time_attr

        after_initialize do
          date = instance_variable_get("@#{date_attr}")
          time = instance_variable_get("@#{time_attr}")
          if date && time
            send("#{datetime_attribute}=", Time.zone.parse("#{date} #{time}"))
          end
        end

        define_method "#{date_attr}" do
          send("#{datetime_attribute}").try(:strftime, "%Y-%m-%d")
        end

        define_method "#{time_attr}" do
          send("#{datetime_attribute}").try(:strftime, "%H:%M")
        end

      end
    end
  end
end