Sometimes, the community will "fix" that by having a newer answer get upvoted beyond the "accepted" answer. E.g. a Python 3.2 answer with more modern syntax in 2014 gets upvoted above the Python 3.1 accepted answer in 2010:
- https://stackoverflow.com/questions/2331592/why-does-datetim...
But that type of "correction" only happens on popular questions. The more obscure questions and answers that are wrong will remain wrong because there are not enough eyeballs and/or widespread expertise to fix them.