Daylight saving begins in NSW, Victoria, South Australia, the ACT and Tasmania this weekend: clocks go forward one hour at 2am on Sunday. If you've got an urgent appointment that morning, I'd suggest setting an old-fashioned alarm clock and not relying on your smartphone.
Last year, we saw a major bug in the iPhone mess up recurring alarms, and it took Apple quite a while to fix the problem. Rather than risking a recurrence, I'd be using a backup system. Computers and other devices should update themselves automatically for the most part, but double-check on Sunday morning as well.