More Details About GoogleBot Visits
Google have changed they way they are reporting site crawls.
Pages that don’t update, i.e. those pages that present a 304 (Not-Modified) response to a If-Modified-Since qualified request, Goolle will provide the date of that request.
“We’ve recently changed the date we show for the cached page to reflect when Googlebot last accessed it (whether the page had changed or not). This should make it easier for you to determine the most recent date Googlebot visited the page“
Good, good.
It would be extra-good if they’d advise more details on when new crawled pages are included in the index, and if not, why not 
Google Inside » GoogleBot With a 304 Response
[...] V7n had some decent insights, but what it comes down to is that GoogleBot will not….well, here’s a quote from the Official Google Webmaster blog. Most people know that Googlebot downloads pages from web servers to crawl the web. Not as many people know that if Googlebot accesses a page and gets a 304 (Not-Modified) response to a If-Modified-Since qualified request, Googlebot doesn’t download the contents of that page. This reduces the bandwidth consumed on your web server. [...]