The nearest expiration date for Singapore Jet Kerosene (Platts) Futures (Jun 2018) is Jul 2, 2018.
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 Singapore Jet Kerosene (Platts) Futures (Jun 2018) before Jul 2, 2018.