I want to update the the code inside `viewDidLoad()` every new day - even if the app is not running - closed or in background. 

```
let Date = NSDate()
let Calendar = NSCalendar.currentCalendar()

var Days = 20
var Hours = 5
var Difference = 0

override func viewDidLoad() {

let FireDate = userCalendar.components(NSCalendarUnit.Hour, fromDate: Date)

if (FireDate.hour == 7) {
      days--
      Difference = (Days / Hours)
    }

}

```

This code does not work how I want it to.