Musk wealth per forbes https://www.forbes.com/real-time-billionaires/ list at

time of writing claim was $250.4bn. So $82.6bn further to go to be a 1/3 trillionaire.

UTC year end time will be the cut off. It is possible that periods when true are missed, so it may well be when there is first a comment here with good evidence that it has happened rather than when it first occurs.