My MacOS 10.12.6 can’t browse the internet “This connction is not private”” on Safari

We haven’t used our laptop, OS Mac for a couple months. Now, when I started up to try to browse the Internet on Safari, it says “this connection is not private”. This website may be impersonating wherever I’m trying to go to steal your personal information you should go back so I always go back. I tried Firefox searching with DuckDuckGo and it says “ did not connect: potential security issue”. It says Firefox detected an issue and would not continue. The website is either misconfigured or your computer Clock is set to the wrong time. Our computer clock we checked is accurate. But every website we try to go to it says there’s an issue with the website. Anybody have any ideas on how to remedy this? Thank you for your help in advance!