Lady Bird celebrates her 18th birthday in 2003, indicating she was born in 1985, but her year of birth on her hospital bracelet shows 1986.
As Lady Bird's mom drives away from the airport near the end of the film, her steering wheel has a black cover on it. In the next shot when she starts crying, it disappears.
When the nun is talking with Lady Bird in the office, about the disturbing posters that she made, the posters keep changing positions in the table, while the camera moves from one character to another.
When Lady Bird is talking to the nun in her office about the musical, when Lady Bird says ''What I'd really like is to be on math Olympiad'', her hair is tucked behind her ear. In the next shot we see her, the same hair is now untucked and at the side of her face.
When Ladybird and Julie first see the nice blue house and stand staring at it, there is about a foot between them. Then the camera switches to show them from the front, and they are touching shoulders. The view then switches back to behind them, and they are a foot apart again.
When Lady Bird jumps out of the moving car, a pole is visible when she opens her door, revealing that the car is being carried on a trailer.
When Lady Bird leaps out of the car at the beginning of the film she has not undone, and is no longer constrained by, the shoulder harness seen in previous shots.
When Lady Bird is in her brother's room in 2002, the PC shows Windows 7 background and task bar from 2009.
When Jenna Walton first appears in 2002, she is shown next to a 2004-model Range Rover.
Upon arriving in New York city in 2003, several of the cabs in the street are 2014 Toyota Camrys.
When Lady Bird's parents pull up to the curb at the airport in 2003, a United sign is visible bearing the company's current globe logo, which it inherited from its 2012 merger with Continental Airlines.
When Lady Bird first meets Kyle he is sitting on a car with a license plate that starts with a 6. A 6 was not used as a first letter on California license plates until 2007.
Lady Bird tells her mother that she's going to get a job and make a lot of money so she never has to speak to her again. If you listen carefully, you can hear Saoirse Ronan's Irish accent slip out a bit.