660
Microsoft formally deprecates the 39-year-old Windows Control Panel
(arstechnica.com)
This is a most excellent place for technology news and articles.
Well. When the OS stops receiving updates there's a whole lot of stuff that stops receiving updates (much of which is the libraries that are being updated with the OS).
Using Windows 10 past the cut-off date is perfectly possible but more and more of the security of your device (and, as it'll be connected to the internet, all other unpatched devices) will be on you, rather than a large company (or a collective of really smart people).