Can I make sure Google always uses my meta description tags for snippets?

Matt's answer:

We have a question from Youser. Youser asks, ‘I use description tags.’ –  meta tags. Still Google search results often start with a date or alter the description snippet. Is there any way of controlling this?’ The short answer is ‘no’ because, in the old days, people would use meta description tags and search engines would dutifully turn that into a description they would show on the web page. But the, the unfortunate fact was there were unscrupulous webmasters who would keep tweaking their description page or put dishonest things in their description meta tags such that users would think the page was about cartoons and they’d land on it and it would be porn. So we reserve the right to describe a website how we think it’s most useful for users. A lot of the time, if you have a good description meta tag, that’s what we’ll use. But if we don’t think that it’s a good description meta tag – for example, it’s nearly empty or it has the word ‘Untitled’ and nothing else or you use the same description meta tag on every single page of your site —  for whatever reason, if we don’t think that’s as useful as a short snippet from on the page, then we’ll use that short snippet from on the page. Or possibly a description from the open directory project or something else that we think is useful. So our guiding principle has to be what we think is best for the users and we don’t always think a meta description from the meta description key – meta tag – is the most useful. So, Youser, I’m sorry to say there’s no way that you as a webmaster can completely control that. One thing you can do is just try to make sure your meta description tags are really useful and that’ll increase the odds of us determining or assessing in our algorithms that we should use that meta description tag. Hope that’s been useful, Youser.

by Matt Cutts - Google's Head of Search Quality Team

Original video: