code: private static Calendar _getThreadCalendar(Locale l, TimeZone tz) {
  	Calendar c = _localeCalendar.get(tz, l);
  	if (tz == null) tz = ThreadLocalPageContext.getTimeZone();
  	c.setTimeZone(tz);
  	return c;
      }
docs: /*
  internally we use a other instance to avoid conflicts