Legal adviser Ali Awad said Saturday on state television that interim president Adly Mansour issued the decree. The elections commission will set a date for the vote, expected to be in April.
Mansour decreed that the decisions of the elections commission be protected from legal challenges, a contentious issue on which two of Egypt's top courts had staked opposing positions.
The law is passed after a transition plan laid out in July after the army ousted President Mohammed Morsi. Military chief Field Marshal Abdel-Fattah el-Sissi is widely expected to declare his candidacy soon, and, if he runs, is forecast to win.