I always go to sleep at 1 to 2 AM during the summer holiday, and wake up at around 9 AM (Sometimes earlier, sometimes a little later). And during the school year, I go to sleep at 11 PM, and wake up at 7 AM.
And yeah, everyone sleep differently, but if they sleep the same amount of hours in every day and go to sleep at the same hour, they'll wake up in the same hour, every day. It's simple math, actually. Let's take me for example.
Wake up- 9 AM.
Go to sleep- A PM.
Awake-17 hours.
Sleeps: 7 hours.
If I'll go to sleep at 2 AM every day, and sleep 7 hours every day, I'll wake up at 9 AM, every day.