What time should I sleep?

My goodness. My sleeping cycles are fucked. I've been sleeping at different times everyday this past week. Today, I spent 6 hours sleeping from 1-7pm and yesterday I slept from 4am-7am. The day before was.... 5pm-1am. Sigh, I'm going crazy here. Fucking split shifts making me all tired and sleeping randomly. I AM SLEEPY BUT I CANT SLEEP NOW BECAUSE I KNOW I WON'T WAKE UP FOR TOMORROW'S MORNING SHIFT. THANK YOU CIRA FOR MAKING ME WORK AT UNGODLY HOURS. Sigh