var expires string
	if !o.Expires.IsZero() {
		expires = o.Expires.UTC().Format(http.TimeFormat)
	}
	return expires
}

// ArchiveInfo returns any saved zip archive meta information.
// It will be decrypted if needed.
func (o *ObjectInfo) ArchiveInfo(h http.Header) []byte {
	if len(o.UserDefined) == 0 {
		return nil
	}
	z, ok := o.UserDefined[archiveInfoMetadataKey]
	if !ok {
		return nil
	}