My windows date is changing to August 3209, somewhat often

I just started getting the problem today. I've been wanting to leave the Insider Program,as I was getting fed up of how much downtime my laptop was experiencing during updates, for about a month now, and this has accelerated my desire. I couldn't open any websites without a warning, and then I looked at Windows Update and it said that I hadn't checked for over 400,000 days. I put the time and date right, and then Windows Update installed updates, and after the last restart, the time and date problem was back. My build is 21390.