need an excuse for work. except ive already told people i wanted it off, boss never gave me the day.?

If you're a decent employee take the day off and say that you do the job when you are there and when your not there it's for a good reason. Management respects people that stand up in a polite and realistic manner (actually they fear losing the good workers/ and it sends them a message that you deserve respect for what you do) Unfortunately they never want to admit that they are at your mercy to make money for them. Life is more important then just a paycheck, you know you can always work somewhere and they know that. If they hassle you about it, look for another job, that one isnt worth staying at. Good employees are hard to find and they are going use you as much as you let them.

If you like having a job, cut with the b.s. excuses. You're right, they already know you wanted it off. They may let you take it if you come up with a primo excuse, but trust me, something will happen that will effect your immediate dismissal.

Just because you want time off doesn't mean you get it. You should be glad you've snowed them into thinking they need you. Keep proving that they don't and that you're unreliable and you'll be easily replaced.