cdm/src/main/java/ucar/nc2/units/DateType.java
public boolean before(Date d) {
    if (isPresent()) return false;
    return date.isBefore(CalendarDate.of(d));
  }
public boolean before(Date d) {
    if (isPresent()) return false;
    return date.isBefore(CalendarDate.of(d));
  }
Is this date before the given date. if isPresent, always false.

@param d test against this date
@return true if this date before the given date