Here is a list of some of the timeline errors. Another example might be the twins saying they haven't won the Quidditch cup since Charlie left... but Charlie is stated to be three years older than Percy and would have graduated the year before Book One. Therefore... of course, they haven't won the cup since he left; there hasn't been any other competition for it since! There was no time for a team without Charlie nor for a slytherin winning streak.

The important stuff all works out, just little things like this that are sort of funny once you notice.