Time Zone Issues

Hi! 

I have set up a MS Bookings page in the Brisbane (GMT + 10) time zone and it works perfectly for that time zone. I have established availability and it works great for others also viewing it in a Brisbane time zone. 

However when someone views the availability from a Perth time zone (GMT + 8), it allows them to book in on an extra day. 

For example, I have set up to be available 11am - 2pm Brisbane time on the 26th and 27th September only for a particular service. This is displaying perfectly for participants who have also selected to view times in a Brisbane time zone. But if you switch to a Perth time zone (which is only 2 hours time difference), it now shows availability on the 25th as well.  

Unfortunately for this project, most people booking in will be from Perth so I would be thrilled for a quick solution. Any help would be massively helpful.