At the end of the film, just after Mark Darcy has come back to see Bridget in the snow. They go upstairs to her flat and as she is in the other room changing, he looks on the table to see her diary open on the 28th/29th/30th. He picks it up and in doing so the camera goes in for a close up and you can see the diary dates are all of a sudden on 10th/11th!!!