John Mueller of Google said on Twitter that we should really ignore the cache date.

I’d ignore the cache date.
— John ☆.o(≧▽≦)o.☆ (@JohnMu) August 11, 2017
If you go to any cache page in Google and read the top message, it tells you when the cache was done by Google. Here is a screen shot of this site in the Google cache showing it was last cached at 11:30:21 GMT today, which was about 45 minutes ago:

Google’s John Mueller once before told us to ignore this cache date when it comes to thinking about when GoogleBot last crawled the site or the page.
But in this case above, John is simply saying ignore the date, it doesn’t help you in any way for SEO purposes.
Obviously, you can use Google Search Console index status reports and the sitemap reports, as well as fetch as Google to get better timelines on Google crawling specific pages. Also, if you are a real nerd, you can use your access logs.
But the Google Cache isn’t a huge help here.
Forum discussion at Twitter.

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