I don't use an alarm clock.
It seems not to matter how late I stay up, I always wake up between 5:30 am to 6:15 am.
I don't bother to start getting ready for work (shower, get dressed, make & eat breakfast, brush teeth, shave) until 7:00 am.
I'm out the door usually between 7:50 am and 8:00 am and usually get to work on time.