class ActiveSupport::TimeWithZone

Time.zone.now.xmlschema # => "2014-12-04T11:02:37-05:00"

format.
Returns a string of the object's date and time in the ISO 8601 standard

def xmlschema(fraction_digits = 0)
  "#{time.strftime(PRECISIONS[fraction_digits.to_i])}#{formatted_offset(true, 'Z')}"
end