BPWrap found an interesting tidbit in Google's international sites: in some cases, the snippets start with a date that is displayed in the same language as the Google interface. For example, Google France displays "9 juil 2006", even if the page contains an English date: "July 09, 2006".
What's even more interesting is that Google doesn't include any date from the page: it tries to detect the most likely candidate for the published date. This should be more accurate than the date when Google first found a web page. Most news sites and blogs display the date when an article has been published and this is an useful information for people who try to find recent news articles or blog posts written in a certain period.
Example of queries that show the published date in Google's snippets: [extended Google snippets], [Microsoft bid for Yahoo], but I'm sure you can find many others.
The new date could replace Google's current estimation that is used in an advanced search option. For web pages that don't include the date when they were created, Google could try to estimate it, based on its content and the recency of the linked web pages.
This is not the only information automatically detected by Google and displayed as part of a snippet: the map plusbox includes the most relevant address identified on a page, a static map and links to directions.