Determine last modified date of a web page
For web pages that do not list their last modified date, you can determine the date and time when a website was last updated, modified, or changed by following the below suggestions. Keep in mind that
Although this site will not give you an exact modified date, allow you to view the history of a page, even if it is offline. Visit the Internet Archive and enter the URL of page or website you're trying to view the modification date.
Note: With dynamic generated content this will not work. Also, newer Internet Browsers with an omnibox also do not support this feature since is more than just an address bar.