gistfile1.rb

module MultiParameterAttributes

  def filter_time(attributes, name)
     attrs = attributes.collect do |key, value|
       if key =~ /^#{Regexp.escape(name.to_s)}\((\d+)(\w)\)$/
         [$1.to_i, value.send("to_#$2")]
       end
     end.compact.sort_by(&:first).map(&:last)
     Time.zone.local(*attrs) unless attrs.empty?
  end

end

class ApplicationController < ActionController::Base
  include MultiParameterAttributes
end

class YourController < ApplicationController
  def your_action
    time = filter_time(params, :my_time_attribute_name)
  end
end

Thanks for that, I have put a modified version up at https://gist.github.com/littleowllabs/5495596 which removes the multi parameter attributes and to set the overall attribute to the time, this allows it to be passed directly in to update_attributes once the filtering has been done.