In any case, you can't count on the data you get from the site.

Some static sites are careless about updating the metas (or the "latest update" info in the body of the page). Some dynamic sites will give you "today's date" every time you visit, despite the lack of any changes in the content.

So, as an exercise, yours is a valid exercise. But if the date info has some critical meaning, be suspicious of what you get.