I really need to change my sleep schedule, but what's the best way to do that?

My sleep schedule right now is that I go to sleep at around 4 AM in the morning, and then get up at 12 PM, sometimes slightly later.
This is obviously not a very ideal schedule, at least not while studying, like I do, so I really need to change this schedule - but what's the best way to do that with minimal harmful effects?
Yesterday I felt kind of tired because I had not slept very well that night, so last night I figured that I should probably fall asleep right away, since I felt so unrested, and I made a point of getting up at 8 AM the next morning - and I did fall asleep for about an hour shortly before midnight, but then woke up because I really needed to go to the bathroom, and then I couldn't fall asleep again.
I lay awake until like 6 AM, and at that point I no longer cared about waking up early, because I was so tired that I seriously felt like I was drunk - it would have been risky for me to walk to school at that point, since I would probably trip and fall somewhere, that's how tired I was, and I also shivered and had a terrible blood circulation, so the thought of taking a ten-minute walk to school at 22° F in the morning felt pretty disgusting as well.
Thankfully I did fall asleep shortly after that, and now it's 2:42 PM and I feel reasonably rested - but I cannot go on like this, and I really need to change my sleep routines.
Do you have any advice?

I have had the same problem..

Try to go to bed very early tonight (8 PM?). Persevere for a couple of days. After a week or so, your body and mind should be accustomed to your new routine.
Eventually you'll wake up early and feel fit.

Make sure your bed is cosy and fresh, put out the lights, no laptop and just try to sleep. I sometimes take a (way too) cold foot bath just before sleepy time.
The cosiness from getting in your warm bed with fresh feet is amazing and puts me to sleep.

Good luck!

Wake up early. Suffer through it for a day, and then go to bed early that next night. Concerning your sleeplessness, you might consider relaxation exercises, meditation, and melatonin.

Thank you for your answers. :content:

I have been considering another method as well lately, though:
do you think it could be alright to simply wake up one hour earlier every morning?
I just realized that I have done like that for the last couple of days: 2 PM on Thursday morning (yeah, that's really late), then 1 PM yesterday and today I got up a few minutes after 12 PM.
So maybe I could keep getting up one hour earlier like this every morning from now on, until I have hit my ideal time?

I have heard that it is apparently better to go to bed and get up one hour later every day and work "clockwise" like that, but that method would collide a lot with my schedule at school and it would also take a really long time, so hopefully working counter-clockwise will be tolerable as well.

Some people have "delayed sleep phase syndrome," where your natural rhythms are not necessarily in tune with the general population. I can relate! I kept exactly the same sleep schedule as you, from 4am to noon, through most of my own school years. If that is your natural sleep period then it's entirely workable as long as you're able to schedule your classes around it. I typically get a "second wind" late at night so I got my best studying done during those quiet hours after midnight, when there were fewer distractions.

However, if you're obliged to take early morning classes or this isn't your body's ideal time to sleep, then you'll need to make some adjustments. Experiment and find out what works... you might even find that sleeping into two separate 3-4 hour periods is more convenient than one 6-8 hour stint (think of the time in between as a really long WBTB!) Changing your sleep pattern is not easy if you're going against the pattern you're programmed with, but I'm convinced it is more important to get enough sleep than to worry about precisely when it happens. If you find yourself consistently lying awake during particular hours, then maybe those aren't your optimal sleep times and you should dedicate them to studying instead.

It's definitely possible to make adjustments if you need to. I've kept 9-5 jobs before, although I hated it. I even spent several semesters attending 8am classes, although I found my motivation for those subjects decreasing more precipitously than they might have. These days I'm able to maintain a later schedule and sleep from around 1:30 to 9:30am comfortably enough, though whenever I find myself in less structured time, the old 4am to noon pattern tends to reassert itself. You'll probably find that there are parts of the day or night that you never ever want to be awake for, and others when you find it almost impossible to fall asleep, so as you re-organize your schedule, try to take those into account.

Yeah, thank you for your answers.
I have actually been pretty successful so far, I woke up naturally at 9 AM this morning and even felt fairly rested, but I decided to sleep until 11 AM because that possibility to become lucid was so tempting, hehe (and I actually did get a False Awakening that lasted for a few seconds, and I was just on the brink of becoming lucid, because I thought everything in my room felt a little strange).
Anyway, that's another major reason why I desire to change my sleep schedule - lucid dreaming.
For some reason it seems like I have a much easier time becoming lucid when I go to bed early and wake up early, and my best success rates tend to be when I go to bed before midnight and wake up without an alarm clock reasonably early, like I did this morning.
Like I said, I had a FA that almost turned into a lucid dream this morning, and on Sunday morning I also had a FA that actually turned into a lucid dream (at least enough to make me react to several inconsistencies and then think "wow, now I have another chance to try doing things in a dream!", although I woke up almost immediately).
I'm not sure if the times I go to sleep has any major effect like that, maybe it just seems that way because I tend to be more serious at those times.

It might also have something to do with the fact that I wrote down all the dreams that I could remember on both of these mornings before I fell asleep again; it seems like the routine "wake up naturally / write down dreams / fall asleep again" is a tremendous trigger for False Awakenings, at least for me, and probably for lots of people.

Hello. I decided to write my question here insted of creating a new topic because I have similar problem with sleep schedule
Since September/October , but unfortunately I didn't manage to work it out yet. The main reason is because my job. I work from 8 am to 4pm. and to get to work takes me some time so I need to get up around 6 am (half past 6 is absolute maximum). Mostly this half an hour I'm using to manage to get up from bed :D First hour at work I feel terrible, I can not concentrate, I can not think straight, when I walk I feel tired like I just finished marathon twice at least :P After 10/11 am it's getting better. After 12 am I feel ok. It could be better but it's ok. After work, around 5/6 pm I am able to fall asleep everywhere. It's the best time for me to sleep. The problem is that when I get up in the middle of night, I couldn't sleep till 6 am, but then I need to go to work. When I stay awake all afternoon which is not simple, I still have trouble falling asleep. It's really weird. From 5 am till 8 am I can fall asleep without a problem but after that time I still feel tired but falling asleep is not that simple. Usually It's like I fall asleep for a few minutes and then I'm waking up. After few hours finally I'm sleeping but it's only 3 to 4 hours a day, which makes my next morning so terrible. It's seems like close circle and I can't find a way how to break it. I've try pills with melatonine and it helps to sleep only for a few nights. Any advice how I can change that sleep schedule to bo more effective ?