My ~3 year old MacBook Pro has done this three times in the past two days. It'll be running fine, usually just typing on a word document or browsing cat videos on the internet, so nothing out of the ordinary. Then, even if it's fully charged, it'll shut down as though it's run out of battery. I have to plug it back in to turn it on again. As soon as it turns back on, I'll find that the clock has reset itself to December 31, 2000 at 7:03pm. Nothing's happened to it lately; I haven't downloaded anything new and there haven't been any physical mishaps either. Unless it's absorbed the time vortex without telling me, I have no idea what's going on! Any suggestions?