@deftypefun {void} {gnutls_global_set_time_function} (gnutls_time_func @var{time_func})
@var{time_func}: it's the system time function, a @code{gnutls_time_func()}  callback.

This is the function where you can override the default system time
function.  The application provided function should behave the same
as the standard function.

@strong{Since:} 2.12.0
@end deftypefun