My neighbor is out again having a party...I find it strange because he yelled at me on a night before when he was working...but it's okay when he wants too?
No, not if he is being loud and rude, that is never okay
They are very strange. I don't understand that selfishness. People work all different days and hours. Of course he doesn't have the nerve to go yell at the people who set off fireworks all night after 10. 
I guess he has no care for anyone but himself