Well, kinda depends. Right now, because of some crazy traveling between DC and China, I've managed to mess up my sleeping schedule a bit.

Usually, 10:30 or 11:00 (PM), especially in the summer. I also found out that I sleep in two chunks when I'm on a proper schedule. I first thought I had a problem until I read about segmented sleep [1].

It seems that there is evidence that before the industrial revolution (and ubiquitous artificial lighting), people would simply wake up in the middle of the night, read, eat or be intimate for 30 minutes and then go back to sleep.

[1]: https://en.wikipedia.org/wiki/Segmented_sleep

The secret to getting up early and it not feeling like torture is going to bed early. I'm getting sleepy around 9pm, and am in bed between 9 and 9.30pm. Depending on my need for sleep I naturally wake up between 5 and 5.30am. Melatonin has initially helped me get to bed early, now it happens naturally.

I am on a similar schedule, and I will start getting tired around 8:45 or so. I'm usually in bed by 9. My first alarm is 4:27 but if I'm particularly tired or don't have anything extra to get done in the morning I will turn that one off and let the one at 4:55 wake me up.