code: public static double call(PageContext pc, double unit) {
  	if (UNIT_NANO == unit) return System.nanoTime();
  	if (UNIT_MICRO == unit) return System.nanoTime() / 1000;
  	if (UNIT_MILLI == unit) return System.currentTimeMillis();
  	return System.currentTimeMillis() / 1000;
      }
docs: this function is only called when the evaluator validates the unit definition on compilation time