If its free, its for me. dlevere. 
Shake Shack may have started out as a little food cart in the middle of Madison Square Park in New York City. But since 2004, Danny Meyer’s humble burger joint has exploded into a widely celebrated, international brand.
Today, the chain opens its 100th location at the Boston Seaport and to celebrate the major milestone, the chain is making the dreams of lucky burger fans come true by giving away free burgers.
But the promotion doesn’t run all day, and there are a few catches. The first 100 guests at all Shack locations worldwide (with the exception of ballpark and stadium outlets) will get one free, single ShackBurger before 12 p.m. Shake Shacks, which usually open at 11 a.m., will be open at 10:30 a.m. Aug. 16.
Shake Shack Locations
Source

Shake Shack may have started out as a little food cart in the middle of Madison Square Park in New York City. But since 2004, Danny Meyer’s humble burger joint has exploded into a widely celebrated, international brand.
Today, the chain opens its 100th location at the Boston Seaport and to celebrate the major milestone, the chain is making the dreams of lucky burger fans come true by giving away free burgers.
But the promotion doesn’t run all day, and there are a few catches. The first 100 guests at all Shack locations worldwide (with the exception of ballpark and stadium outlets) will get one free, single ShackBurger before 12 p.m. Shake Shacks, which usually open at 11 a.m., will be open at 10:30 a.m. Aug. 16.
Shake Shack Locations
Source