List of accepted papers: Why do notifications take 10 more days?
Most likely, the program committee needs some additional time to edit reviews and provide a summary of the PC's discussion of the paper.  Reviews may require editing to remove bugs (for example, if a reviewer misinterpreted a result, but the misunderstanding was cleared up in discussion), or to professionalize the language (a reviewer might have described an author as a jerk or worse), or to remove references to other submissions under review need to be purged.