UIDatePicker - Difference between 2 dates in hours:minutes

I have this

NSDate *date1Val = date1.date;
NSDate *date2Val = date2.date;
NSTimeInterval interval = [date2Val timeIntervalSinceDate:date1Val];
int hours = (int)interval / 3600;             // integer div开发者_Python百科ision to get the hours part
int minutes = (interval - (hours*3600)) / 60; // interval minus hours part (in seconds) divided by 60 yields minutes
NSString *timeDiff = [NSString stringWithFormat:@"%d:%d", hours, minutes];

but it doesnt show me correct date - for 24 hours it says 23:57 no idea why

When selecting a date using a UIDatePicker in date only mode the time that was set in date + time mode is also present in the supplied date. You can go into IB, switch the UIDatePickers to Date & Time mode and make sure that the hour and minute are the same.