static LongRange dateStructureToTimestampRange(DateStructures.SomeDate d) {
  ret dateStructureToTimestampRange(d, localTimeZone(), now(), true);
}

static LongRange dateStructureToTimestampRange(DateStructures.SomeDate d, TimeZone tz, long now, bool assumeFuture) {
  delegate Day to DateStructures.
  delegate Month to DateStructures.
  delegate Year to DateStructures.
  delegate CurrentWeekPlus to DateStructures.
  delegate CurrentMonthPlus to DateStructures.
  delegate CurrentYearPlus to DateStructures.
  delegate Weekday to DateStructures.
  delegate TodayPlus to DateStructures.
  
  // year
  
  if (d instanceof CurrentYearPlus)
    d = new Year(year(now) + ((CurrentYearPlus) d).nYears);
  if (d cast Year)
    ret longRange(yearToTimestamp(d.year, tz), yearToTimestamp(d.year+1, tz));
    
  // month
  
  if (d instanceof CurrentMonthPlus)
    d = new Month(month(now) + ((CurrentMonthPlus) d).nMonths, ((CurrentMonthPlus) d).year);
  if (d instanceof Month)
    ret longRange(yearAndMonthToTimestamp(((Year) d.year).year, d.month);

  fail("dateStructureToTimestampRange: unknown type" + d);
}