Other mistake: On the back cover of Scream 3 in the Scream trilogy on DVD, the town of the original killings is referred to as Greensboro twice. The correct name of the town is Woodsboro, of course.
Other mistake: When Sidney is on the set with her mother's covered body, it rises up and reaches for her, speaking in her mom's voice. Sidney calls out for Dewey before climbing out of the window. However, when she's grabbed, she yells out her own name: Sidney.
Answer: Not expressly, though it could have been the date of some significant event (December of 1988) but someone as security-conscious as Sydney now is wouldn't be stupid enough to have her code be something that could be guessed.