// which is allowed for by the PAX specification, but not always portable.
func parsePAXTime(s string) (time.Time, error) {
	const maxNanoSecondDigits = 9

	// Split string into seconds and sub-seconds parts.
	ss, sn, _ := strings.Cut(s, ".")

	// Parse the seconds.
	secs, err := strconv.ParseInt(ss, 10, 64)
	if err != nil {
		return time.Time{}, ErrHeader
	}
	if len(sn) == 0 {