DateTime.iso8601 ou to_json não retorna UTC com “Z”
ActiveSupport :: TimeWithZone tem alguns comportamentos interessantes.
require 'active_support/core_ext'
=> true
ActiveSupport.use_standard_json_time_format
=> true
DateTime.new(2013, 5, 28).to_json
=> ""2013-05-28T00:00:00+00:00""
DateTime.new(2013, 5, 28).in_time_zone('UTC').to_json
=> ""2013-05-28T00:00:00Z""""
ActiveSupport.use_standard_json_time_format = false
=> false
DateTime.new(2013