How can I be less tired in the morning?

During the weekend, I naturally wake up at 8 or 9am, no matter how late I went to bed – usually around 2 or 3am. So I average about 6 or 7 hours of sleep per night during the weekend, but I never have trouble getting out of bed – I just naturally wake up and decide to start my day.

During the week though, I have to wake up at 7am to get ready for work. It seems like no matter how many hours of sleep I get the night before, I am always completely groggy, hit the snooze button 3 times, and can not bring myself to get out of bed. Whether I go to bed at 11, 12, or even 1am, I am never ready to wake up at 7. I have never naturally woken up at 7 or felt good and refreshed like I do during the weekend.

Why is it that I can get 7 hours of sleep from 2am to 9am and feel great, but from 12am to 7am I feel awful? How can I prevent this? Is it a dietary thing? Is there some sort of vitamin I should be taking? I imagine it has something to do with circadian rhythms, but how would I fix it?