Patience, masses of patience, really huge colossal mountains of patience, my sleep pattern rotates (adding or subtracting several hours a day from the spot at which I can sleep) so with patience it will eventually reach the right time again and will stabilise there until the next upset.
I'm glad I'm patient, if I wasn't I'd be (more) stark raving bonkers by now
Watching the early dawn light helps to reset my body clock. Avoidance of sugar, caffeine (soft drinks, tea, coffee, redbull, chocolate etc.) is also a good idea. If your fond of exercise do some as that will help you to be tired at the right time.
I heard anecdotal evidence that cabbage has a soporific effect (the story of peter rabbit) and have personally found skin contact with lavender oil in water to induce sleep.
Aside from all that, as you are awake at uncommon hours you may as well make the most of it see what goes on during those times