Nasdaq recommends that listed issuers wanting to issue material news after the regular market close at 4:00 p.m. ET wait until at least 4:01 p.m. ET, and preferably until 4:05 p.m. ET, to disclose that news, unless there are specific circumstances where the issuer needs to act immediately.

This rule gives shorts and day traders an advantage of manipulating the stock during trading hours. My opinion, screw them, all markets should be open to news at any time so these gamblers can get burnt.