Update ViewController.swift in this tutorial. "How to Build a Countdown App - Swift 3 in less than 10 minutes" -> Tutorial Link: https://goo.gl/0gCby9

ViewController.swift

//
//  ViewController.swift
//  gerisayim.net
//
//  Created by Harun Memur on 27/11/2016.
//  Copyright © 2016 Harun Memur.
//

// Swift Version: 3.0.1
// Xcode Version 8.1
import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var timeLabel: UILabel!

    let formatter = DateFormatter()
    let userCleander = Calendar.current;
    let requestedComponent : Set<Calendar.Component> = [
        Calendar.Component.month,
        Calendar.Component.day,
        Calendar.Component.hour,
        Calendar.Component.minute,
        Calendar.Component.second
    ]

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        let timer = Timer.scheduledTimer(timeInterval: 1.0, target: self, selector: #selector(timePrinter), userInfo: nil, repeats: true)

        timer.fire()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func timeCalculator(dateFormat: String, endTime: String, startTime: Date = Date()) -> DateComponents {
        formatter.dateFormat = dateFormat
        let _startTime = startTime
        let _endTime = formatter.date(from: endTime)
        
        let timeDifference = userCleander.dateComponents(requestedComponent, from: _startTime, to: _endTime!)
        return timeDifference
    }
    
    @objc func timePrinter() -> Void {
        let time = timeCalculator(dateFormat: "MM/dd/yyyy hh:mm:ss a", endTime: "12/25/2018 12:00:00 a")
        timeLabel.text = "\(time.month!) Months \(time.day!) Days \(time.minute!) Minutes \(time.second!) Seconds"
    }

}

it doesn't work

it works fine, just change 2016 to 2017 and make sure timeLabel.text is connected correctly between storyboard and ViewController.

I changed the date to 05/19/2018 and it returns this error: (Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value) on this line of code: let timeDifference = userCleander.dateComponents(requestedComponent, from: _startTime, to: _endTime!)

Hi @mannyd209, check your outlets please.