format.mustNotBe(FormatGNU)
		}
		isMtime := paxKey == paxMtime
		fitsOctal := fitsInOctal(size, ts.Unix())
		if (isMtime && !fitsOctal) || !isMtime {
			whyNoUSTAR = fmt.Sprintf("USTAR cannot encode %s=%v", name, ts)
			format.mustNotBe(FormatUSTAR)
		}
		needsNano := ts.Nanosecond() != 0
		if !isMtime || !fitsOctal || needsNano {

		case paxGid:
			id64, err = strconv.ParseInt(v, 10, 64)
			hdr.Gid = int(id64) // Integer overflow possible
		case paxAtime:
			hdr.AccessTime, err = parsePAXTime(v)
		case paxMtime:
			hdr.ModTime, err = parsePAXTime(v)
		case paxCtime:
			hdr.ChangeTime, err = parsePAXTime(v)
		case paxSize:
			hdr.Size, err = strconv.ParseInt(v, 10, 64)
		default: