The nearest expiration date for PJM JCPL Zone Peak Calendar-Month Day-Ahead LMP Futures (Sep 2014) is Sep 30, 2014.
The best time to sell a futures contract is when you've already made money on the investment, but still have plenty of time left before the expiration date. Thus, a good option would be to sell PJM JCPL Zone Peak Calendar-Month Day-Ahead LMP Futures (Sep 2014) before Sep 30, 2014.