EDIT: I changed the date, i initially had no idea that fnaf 1 actually gives a concrete date for this
June 26th 1983
A Nissan AD with a family inside was going around the parking lot, with the driver looking for a place to park. He finally found one, and the family exited the car.
Father: I don't really get the appeal of this place. The animatronics look a little... Off.
There were 2 kids present. Kid nr. 1 was around 10 years old, and was wearing a striped shirt and a bandana on his head. Kid nr. 2 was around 16, and was wearing a blank red T-Shirt.
Kid 1: Don't be so grumpy, it's gonna be fun!
Kid 2: Sure. Just don't go too far away.
The second kid was his brother, and was there to make sure his little brother doesn't get lost, or worse.
They were standing next to a one-story building, with a sign which, in big, bold letters, exclaimed "Freddy Fazbear's Pizza". They entered the building, while another car, this time an old 1972 Cadillac Sedan deVille, purple-colored, was also entering the parking lot.
They walked into the dining area. It was a huge room, and was full of people.
After a few hours of eating pizza.
Kid 2: Alright, I need to go for a few minutes. Don't wander too far away.
He goes to the men's bathroom, an when he's about to go back, an alarm goes off somewhere and the employees start evacuating the building.
Kid 2: Huh? What's going on?
He walks around the now mostly empty building. He then sees a figure at the end of a hallway.
Kid 2: Hello? Have you seen my brother? He's around 10 years old.
The figure laughs, and the kid can now make out that the person is wearing a purple night guard uniform. The guard then pulls out a gun.
Purple guy: You were too late to save him.
6 hours later, at a Hospital, the kid wakes up next to a doctor, and realises he has bandages around his head.
Doctor: Hello. Do you remember your name?
Kid 2: Y-yes. Jeremy Fitzgerald.
8 November 1987
Foxy: Worse. He's my brother.