If I adjust the
meta:description in my page for SEO, how many days would google, yahoo, bing search engine update?
BTW: if my sitemap set this page's
According to Matt Cutts (sorry I don't have the link to the video) he says that if Google knows your website is updated frequently then they will crawl it in "a couple of days". If your site hardly changes then it'll take a lot longer.
My personal experience is that a meta description or page title change can be crawled within a few hours on Google. I added a meta description to a clients site at about 11pm one night. In the morning (roughly 8am) I searched for them on Google and their meta description appeared.
However, Bing isn't the same. Bing will take a few more days (even a week) to update.
It depends mostly on how frequently your page is being crawled by the search engines, but 2-3 days at most.
In my experience, the better your page is ranked in the search engines the more frequently it is crawled.
With Google Webmasters you can see how frequently your page has been crawled by google.