UIpopovercontroller shows at wrong position with Arrowdirectionup

I am in a strange situation the problem is that i am showing a UIpopovercontroller which contains a datepicker and a done button. But when i show this with arrowdirectionup then it get by default Y direction from some where i tested it with x=0 and y=0 then x is working but 开发者_JAVA百科the Y is still get value i dont know why it not working.

And if change the arrowdirection to down, right or left then it displayed at the right given position like 0,0.

datePopOver = [[UIPopoverController alloc] initWithContentViewController:datePopoverView];
[datePopOver setPopoverContentSize:CGSizeMake(307, 247)];
[datePopOver presentPopoverFromRect:CGRectMake(0, 0, 307, 247) inView:self.view permittedArrowDirections:UIPopoverArrowDirectionUp animated:YES];