All Auctiva accounts are initially set to PST by default, which is about 12 hours behind the main Australian time zone. Since the listings you are scheduling are one hour off, it sounds like you either need to change your preferred time zone setting within Auctiva or enable the "Adjust for Daylight Savings" time setting.
The options to do both of these things can be found by clicking the "Account Settings" link under the "My Account" tab within your account. The "Preferred Time Zone" drop-down menu is in the "Listing Management" section and the "Adjust for Daylight Savings" time box is right below it.
If you need any further assistance with this issue, please feel free to contact our customer support team using the web form on the following page of our site: http://www.auctiva.com/help/requesthelp.aspx