Wendy's giving away free cheeseburgers every day through Sept. 30

National Cheeseburger Day was Sept. 18, but Wendy's announced it is celebrating the holiday all month long by offering its Dave’s Single burger for free with the purchase of any other menu item.

The offer — valid through Sept. 30 at all Long Island locations — is redeemable via the chain’s mobile app only, and can be used once per customer, per day.

The quarter-pounder is topped with American cheese, lettuce, tomato, pickle, ketchup, mayo and onion and is served on a toasted bun.