I change my schedule by partying hard a Saturday night and staying awake (not sleeping since getting back from partying) most of Sunday until about 8:30pm at which point I take a hot bath, put on an eye mask and drop dead in bed. I'm usually awake at around 4:30 or 5am Monday. After that I just condition myself to be sleepy when I go into my room. If I have something to do at home after work, I do so out of the room. I basically condition myself to be sleepy the moment I enter my dark room at night by just going to sleep really early. After that I'm AOK to sleep around 9 and wake up at 3 or 4am and get shit done in the hours before going to work. Then when I get home I have time to watch a movie and check emails before collapsing in bed.

I am 28 so I might add that you might want to adjust such a process according to your age and responsibilities. Hell you might not like to party like I do. If that's the case, substitute the partying for reading a good book, working on your startup, testing to see how waterboarding and CIA sleep depravation works, or just having a crapload of coffee.

Also, I know you specifically mentioned no drugs, BUT it might be easier to take a Benadryl at 6pm and use that to wake up early the next day. You will feel a bit drudgey the next day but that's fixed with the first cuppa-o-joe of the day.

Hope I helped :)

PS: I know my methods aren't the healthiest, but they do work for me and I keep in shape with good nutrition and exercise, so that's that.