From the press release:
The Chicago Cubs today announced Wednesday, September 30, as the make-up date for their August 16 postponement against the Pittsburgh Pirates. The game will start at 1:05 p.m.
All tickets for the postponed game from August 16 will be honored at the gates on September 30 at 1:05 p.m. There is no need for fans to exchange tickets.
The 1:05 p.m. make-up game is now part of a day-night, separate admission doubleheader. The regularly scheduled game will follow at 7:05 p.m.
Gates will open at 10:35 a.m. for the 1:05 p.m. game and at 6:05 p.m. for the 7:05 p.m. contest.
Fans unable to attend the September 30 make-up game may request a refund by sending their tickets to the Wrigley Field Ticket Office at 1060 W. Addison St., Chicago, IL 60613 or by visiting the Wrigley Field ticket windows during business hours. All refunds must be requested before September 4.
UPDATE: Have been informed by the Cubs that the gates will open at 11:35, not 10:35, for the day game.