I keep getting certificate errors and websites not loading correctly or really slow

It all started when I changed the "Inteet Time Settings" server to something else because it didn't get the correct time.

After I have found a correct server the time was correct (also is now), and now almost every site I get into that has https is displaying error about the certificate:

Your coection is not secure

I am using Firefox and it happens in Explorer and Chrome too..

My computer is new (bought it 2 month ago) and I just installed windows 10 (clean install).

What could be the problem?

I don't have the tools to test the CMOS (saw an answer about that) and I don't think that it is it because the computer is new..

I tried manually change the time back to 2015 and back to 2016 but nothing happens.

Thanks in advance!

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