The platform uses the time zone set on your device. Every time you see on the trading screen, including the clock, the expiry times and your history, is shown in your local time, and so is the Transaction History in your client area. If your device is set to Japan time, you see Japan time.
There's no setting to change the time zone on the platform itself. To see a different time zone, change it on your device.
Trading hours in these articles are given in UTC, with Japan time alongside. Japan time is UTC plus 9 hours all year round.
Related: Trading hours · Expiry times · Holiday trading hours