I made some changes recently to my website that were substantial.
My page rank for my business's name is now #1.
However, Google shows wrong information in the search results, as do Bing and Yahoo.
So how long?
It varies. Sites like Stackoverflow will see changes reflected seemingly immediately while smaller sites may wait days or even weeks for the changes to be represented in the search results. See this answer for why.
I know it's anywhere between a day and 6 weeks usually. The exact time depends on your history with google (i'm not all that familiar with bing (with also gives yahoo results)). If your site changed often in the past google will reindex relatively quickly, if google didn't see any changes in the past 76 years it won't reindex very fast. my own site was reindexed by google after about a week after submitting the sitemap to google.