Drink some coffee or such through out the day to make sure you stay up all day. It'll be hell, but it'll work.
You might have to do it a couple times. If you've been going to bed at 3 for a while, you'll naturally be staying up until 3.
I think if you've only been staying up until 3, you'd have better luck taking some benadryl about a half hour to an hour before the time you want to be going to bed and repeat that for a couple nights to establish a new pattern.
As far as I know, the time you're sleeping isn't going to be too bad for your health. What is is sleep deprivation. So if you've got no problem sleeping in 'till 10 every day, no need to worry about it.