If you buy one such as a hamburger you get another one for free "McDonald's Hamburger Day"

Precisely it is not a hamburger but a "hamburger free ticket" can be obtained, it is quite a heavy plan.

Period and other details from the following.
In commemoration of the day of opening the first McDonald's Japan store
"McDonald's Hamburger Day" implemented
On Monday, July 12 (Sat) and 13 (Sun), at McDonald's nationwide
Per burgers purchase, "Hamburger free ticket" gift!

The period is 2 days from 0 o'clock on Saturday, July 12 (Sat) to July 13 (Sunday) at 24 o'clock. Every time you buy one kind of burger at McDonald's store, you can receive one "Hamburger Free Ticket".

"Hamburger free ticket" exchange period is 14 days from July 14 (Monday) 10:30 to July 27 (Sunday) 24 o'clock. However, up to two hamburgers are exchanged for each ticket by free ticket. Also, it is said that the morning Mac sale time zone can not be exchanged with a hamburger.

The "Hamburger free ticket" gift item is "Burger kind", but it seems to include Mac Lap · Hot Cake · Petit Pan Cake · Chicken Mack Nugget · Salad dish.