@deftypefun {int} {gnutls_x509_crq_get_private_key_usage_period} (gnutls_x509_crq_t @var{crq}, time_t * @var{activation}, time_t * @var{expiration}, unsigned int * @var{critical})
@var{crq}: should contain a @code{gnutls_x509_crq_t}  type

@var{activation}: The activation time

@var{expiration}: The expiration time

@var{critical}: the extension status

This function will return the expiration and activation
times of the private key of the certificate.

@strong{Returns:} On success, @code{GNUTLS_E_SUCCESS}  (0) is returned, @code{GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE} 
if the extension is not present, otherwise a negative error value.
@end deftypefun