OOOOOH. I've had that before. It's going to be REALLY hard, but if you want to reset your sleep patterns, there's a way to do it. It takes about a month and you have to be vigilantly rigid about things. It helps if you have a roommate or loved one that can help you with waking up by certain times. It's going to be the hardest part.

First, regardless of how tired you are, force yourself to stay awake during the day. Go be active. Get social. The more you move and interact, the less likely it is you'll fall asleep. For the first week do everything you can to keep yourself from sleeping every couple of days. If you start on Sunday, don't go to bed until monday, and only allow yourself no more than 7 hours of sleep. If you feel like you're going to pass out during the day, take an hour nap, and make sure you wake up. Each night of sleep, set your clock to wake you at a decent hour in the morning - say something between 8:30 and 9:30 am. 10:30 in the morning is the latest I'd give it, as that's pushing the boundary into waking up in noonday.

After a week of this, you can ease off the forcing yourself to be awake, but increase the level of activity you're doing during the day. Maybe go for a jog or walk in the evening, and keep active. You also need to be making sure you're eating healthy. I know this will be more difficult with the depression, but you gotta force yourself to get out if even just to keep moving. Do this for a week, keeping your alarm set to the same decent hour and making sure you're laying down for bed the same time every night. You may want to lay down between 10 and 11 p.m. No later than midnight, if you're getting up around 9.

For the third and fourth week, keep your activity, and get an evening routine together. Getting the same activities done right before you lay down for bed will train your mind to relate sleep with the evening activities.

The basic concept here is to first force your body out of its current sleep cycle by removing the sleep altogether. Then, allow sleep to return but only in the evening. You reinforce this by putting a limit on your sleep and always waking up at the same time. The exercise encourages production of seratonin, which will keep you awake during the day, and you'll be tired come night time. The evening routine cements the evening-means-sleep connection as a final tactic.