how to use the function "nx_sntp_client_set_time_update_notify"

Dear Forum

I've confirmed this callback(time_update_cb) executed immediately after initializing.

I thought that it would be executed periodically, but callback function was not executed. 

How can I get callback periodically?

nx_sntp_client_set_time_update_notify(&g_sntp_client0, time_update_cb);

Thanks