How To Display Time Until A Certain Date in iPhone Programming?

I was wondering if you someone could help me with somehow showing the exact time (months, days, minutes, even seconds) until an exact date in a text label in iPhone programming.

I’m hoping that when the app is launched, it shows in a label the amount of time from the minute it is opened until a certain date, and it displays in days, hours, minutes, and seconds..

Please include the code…or sample code.