As the chart is in the 4h timeframe the time of each settlement is off. So note here that Cboe's expire at 21:00 (ukGMT) or 16:00 (EST); two days before the third Friday of each month. And CME's expire at 16:00 (ukGMT) or 11:00 (EST); on the last Friday of each month.
October 1st marked the beginning of Q4.
Upcoming settlements in October:
- Cboe's settle on Wednesday October 17th, 2018
- CME's settle on Friday October 26th, 2018