docs: public final void setDateTimeFlag(int field, boolean value)
  	{
  		if (field == CLOCK_SYNC) {
  			setBitEx(0, QUALITY, value);
  			return;
  		}
  		final int f = field - WORKDAY;
  		if (f < 0 || f >= FLAG_MASKS.length)
  			throw new KNXIllegalArgumentException("illegal field");
  		setBit(0, FLAG_MASKS[f], value);
  	}