code: public static String getUtc(final String time,
                                final String tzid) throws TimezonesException {
      return getTimezones().calculateUtc(time, tzid);
    }
docs: Given a String time value and a possibly null tzid,
  will return a UTC formatted value. The supplied time should be of the
  form yyyyMMdd or yyyyMMddThhmmss or yyyyMMddThhmmssZ
  
  <p>The last form will be returned untouched, it's already UTC.
  
  <p>the first will have T000000 appended to the parameter value then the
  first and second will be converted to the equivalent UTC time.
  
  <p>The returned value is used internally as a value for indexes and
  recurrence ids.
  
  <p>tz null mean this is local or floating time
  
  @param time  String time to convert.
  @param tzid  String tzid.
  @return String always of form yyyyMMddThhmmssZ
  @throws TimezonesException for bad parameters or timezone