In the scene after all of the power is shut down and they see "system ready" on the computer screen, there is a slip-up. When the character played by Samuel L. Jackson talks about the mishaps in Disneyland when it was first opened, he says it opened in 1956 but it actually opened in 1955.
This slip-up actually occurs a while after they see 'system ready' on the computer screen, it is when they are in the emergency bunker and Ray Arnold (Samuel L. Jackson) has gone to turn on the power. Therefore it is not he who says this, It is John Hammond (Richard Attenborough).
Thankyou Spudman. If you are going to put a slip-up in, make sure it is correct. Spudman is right. They are in the bunker and John Hammond says the Disneyland line. Mr Arnold is off being eaten by raptors.