code: func extractTimeRange(min, max *time.Time) (mint, maxt time.Time, err error) {
  	if min == nil {
  		mint = minTime
  	} else {
  		mint = *min
  	}
  	if max == nil {
  		maxt = maxTime
  	} else {
  		maxt = *max
  	}
  	if mint.After(maxt) {
  		return mint, maxt, errors.Errorf("min time must be before or equal to max time")
  	}
  	return mint, maxt, nil
  }
docs: // extractTimeRange returns minimum and maximum timestamp in milliseconds as
  // provided by the time range. It defaults either boundary to the minimum and maximum
  // possible value.