Why is my computer behaving erratically?

A few days ago, I was using the computer and it completely crashed; it turned off completely and the charger stopped working. It took about ten minutes to turn it back on and I got a message saying "The clock on this computer is set incorrectly. This may cause some applications to behave erratically." The charger kicked back in about a minute later. The computer crashed AGAIN a few minutes later and the charger stopped again. I deleted/emptied all of my downloads and it worked for about two days. Now it's crashed once again and the charger doesn't work AT ALL anymore! No matter what outlet I use, the computer won't charge and there is no damage on the power cord. What can I do? 😮