The Board of Studies notifies schools each year when they release a Draft Timetable - schools will usually consult with their Year 12 students to see if there are any clashes etc.
The Office of the Board of Studies will then release an official Timetable - each Year 12 student is required to sign to verify that they receive it, and this is usually done within a week of its release.
In addition, the boredofstudies.org usually also posts a notification up on our site as soon as we get whiff of the timetable.
I wouldn't worry too much. Previous years indicate you won't know until early next term.