You are not sleeping 'late' - many consider 8 hours to be appropriate for the majority of the human race. It would be late if you we sleeping from midnight to midday...You are only time-shifted. So as regards your question on detoxing - it is irrelevant.
If you want to sleep from midnight to 8am, this becomes a relatively simple problem of managing your body clock by four hours - as many jet-lagged international travellers have to do on a regular basis.
First and foremost, you need to get used to going to bed before midnight, whether or not you feel tired. This is all about changing your routine. If you do not even go to bed until 4am you certainly won't go to sleep before then!
Then have your alarm set for 8am - this will be a shock to the system for the first few days as you will only have had a few hours sleep, but this will help persuade you to go to bed earlier.
If you are in a country where the sun is bright in the morning, have your curtains open - we are hard-wired to become alert with the rising sun, in general, so this helps you wake naturally.
Avoid caffeine. Seriously. Until you are settled in the correct time slot, caffeine confuses your responses to tiredness.
Exercise well. This just helps your body do most things well - digestion, metabolism, sleep etc.
Eat healthy foods. Junk food doesn't always play well with your body, and heavy meals late at night are also not conducive to a good sleep.