@deftypefun {int} {gnutls_x509_ext_export_private_key_usage_period} (time_t @var{activation}, time_t @var{expiration}, gnutls_datum_t * @var{ext})
@var{activation}: The activation time

@var{expiration}: The expiration time

@var{ext}: The DER-encoded extension data; must be freed using @code{gnutls_free()} .

This function will convert the periods provided to a private key
usage DER encoded extension (2.5.29.16).
The  @code{ext} data will be allocated using
@code{gnutls_malloc()} .

@strong{Returns:} On success, @code{GNUTLS_E_SUCCESS}  (0) is returned, otherwise a
negative error value.

@strong{Since:} 3.3.0
@end deftypefun