Yes, there is. The Shulchan Aruch, Yoreh Deah, 344:20, writes that it is correct to go to the grave on the thirtieth day. In general, the custom is not to go to the grave during the first year of a person's passing with the exception of the day that sitting shiva ends, the thirtieth day, and the unveiling of the tombstone - which usually occurs on one of those days or on the yahrzeit.