7am in Australia GMT+10 (East Coast, which includes Brisbane)
5am in Singapore, China etc GMT+8
12:00am in Russia MSK (eg Moscow) GMT+3
9pm (previous day) in UK (eg London) GMT+0
5pm (previous day) in USA EDT (eg New York) GMT-4
2pm (previous day) in USA PDT (eg Los Angeles) GMT-7
Seems a strange time to schedule a meeting of international partners, since much of the world will be outside business hours at that time.
New Zealand is where Cryptopia was based, I guess it follows that the company running the show can also dictate terms. Having said that, it could be a combination of things such as the number of traders in the USA Vs other parts of the world. It could also be that traders will log in at various times (including midnight) given the global nature of the exchange.
Don't forget the Northern Hemisphere are observing daylight savings in many places, so some of those times may not be 100% correct - UK for example.