The 59-year-old Gary was convicted in 1986 of killing three women in the 1970s.
Muscogee Superior Court Judge Robert Johnston signed the order for Gary's execution on Thursday. The Department of Corrections announced the date on Friday for the execution by lethal injection at the state prison at Jackson.
Gary was arrested in 1984. In 1986, he was convicted in three of the city's seven "stocking strangler" slayings, so-called because the victims were strangled with their own stockings.
The U.S. Supreme Court rejected an appeal by Gary this week.