Instructions
Select "System" from the Settings tab on your Xbox 360 dashboard.
Select "Console Settings" from the menu and then "Clock."
Select "Date and Time" and change the date on your Xbox 360 to any day in August 2012.
Load "The Amazing Spider-Man" and you will unlock the party hat after loading your saved game.
Select the party hat from your closet when you are in Spider-Man's in-game apartment. The party hat is on the shelf above the costumes in the closet and is usable with any other costume.