The Australian stock market is open from 10:00 to 16:00 Monday to Friday, Australian Eastern Daylight Time. The Australian market is open for 6 hours per day.
I think GGP will have missed the June ASX200 rebalance which I believe occurs after the 3rd Friday of the rebalance month. Next following rebalance would be in September. https://www.marketindex.com.au/methodology
Checking out Google Maps, I hadn't realised that there is a decent sized Telfer Airport. I knew they'd need something - but I was thinking it'd be more of an airstrip/airfield.