Q:

How calculate time from current time?

I have design an application in which i am have three text field in which i am giving my time like as 10:10 PM. Now problem is that i want to calculate time difference between current time and entered time. How calculate time? 

A:

Depending what you mean by "entered time" you will most likely need to look at NSDateFormatter and parse the entered time into a usable form, then get a date using NSDate (i.e. NSDate * now = [NSDate date];) and do whatever math you need using the methods available in `NSDate'.
If you are just determining the difference between entered date and now this method would suit you:
- (NSTimeInterval)timeIntervalSinceNow

