if zone < 0 {
		b = append(b, '-')
		zone = -zone
	} else {
		b = append(b, '+')
	}
	b = appendInt(b, zone/60, 2)
	b = append(b, ':')
	b = appendInt(b, zone%60, 2)
	return b
}

func (t Time) appendStrictRFC3339(b []byte) ([]byte, error) {
	n0 := len(b)
	b = t.appendFormatRFC3339(b, true)

	// Not all valid Go timestamps can be serialized as valid RFC 3339.
	// Explicitly check for these edge cases.