Did you remove the positive battery cable to clean off the terminal? That would explain the clock getting reset.

Sounds like it could be your starter. They start clicking a bit before going totally bad. They will work intermittently then go kaput altoghether. However, a weak battery can give similar symptoms so you'll want to eliminate that possibility first.

You can go to a parts store like Autozone to get your battery checked for free. They can check alternators and starters as well but they usually have to do this with the part out of the car.