Why is it called Five Nights at Freddy's if there are seven nights?

Answer 1

The job was to cover 'Five Nights' to get your paycheque on the Friday. Night 6 and Custom Night are for bonus overtime.

Answer 2

The game is called "Five Nights at Freddy's" because the main gameplay consists of surviving for five consecutive nights at the Freddy Fazbear's Pizza. The additional nights, known as Night 6 and Night 7, are bonus challenges for players who want to continue testing their skills after completing the main game.

Answer 3

Five Nights at Freddy's was originally made to only have five nights, though they decided to add a 6th night and custom night so you could do bonus when you complete the game.