As usual, 1stGenCRXer is right on. It sounds like a main relay.

When you turn the key to ON (not START), you should hear the fuel pump kick in. Listen for it at night, when it starts okay, so you'll you'll know what to listen for. Then, listen for it again during the day, when it doesn't start. If you DON'T hear it during the day, it's probably a bad main relay.