You may want to know when did Google’s spiders last crawled your website for several reasons. For instance, if you recently added some new pages to your website, and they are not appearing in Google search results yet, you may want to check if Google recently crawled your site at all. Because if it did not, then it doesn’t even know about those pages. In this case, you should change the crawl rate of your website in Google webmaster tools. You also need to ping your website url and get some fresh back links.
You may also want to check the last indexing date of a website by Google before you decide to write a guest post on it. This is because if the last crawl date is very old, then probably its not a good idea to guest post as the (back)link to your website will not be seen by Google in near future.
It very easy to find the last crawl date and time of any website. Just open google.com, and type,
This will show you the cached copy of this website in Google’s database. At the top, you can see the last time when Google’s spiders crawled this website.
This Google query is not limited to root domains. You can also check the last crawl time and date of a single webpage using the same query.