code: func (p GTLDPeriod) Valid(when time.Time) error {
  	// NOTE: We can throw away the errors from time.Parse in this function because
  	// the zlint-gtld-update command only writes entries to the generated gTLD map
  	// after the dates have been verified as parseable
  	notBefore, _ := time.Parse(GTLDPeriodDateFormat, p.DelegationDate)
  	if when.Before(notBefore) {
  		return fmt.Errorf(`gTLD ".%s" is not valid until %s`,
  			p.GTLD, p.DelegationDate)
  	}
  	// The removal date may be empty. We only need to check `when` against the
  	// removal when it isn't empty
  	if p.RemovalDate != "" {
  		notAfter, _ := time.Parse(GTLDPeriodDateFormat, p.RemovalDate)
  		if when.After(notAfter) {
  			return fmt.Errorf(`gTLD ".%s" is not valid after %s`,
  				p.GTLD, p.RemovalDate)
  		}
  	}
  	return nil
  }
docs: // Valid determines if the provided `when` time is within the GTLDPeriod for the
  // gTLD. E.g. whether a certificate issued at `when` with a subject identifier
  // using the specified gTLD can be considered a valid use of the gTLD.