Format timer label to hours:minutes:seconds in Swift

Your calculations are all wrong.

let hours = Int(time) / 3600
let minutes = Int(time) / 60 % 60
let seconds = Int(time) % 60
return String(format:"%02i:%02i:%02i", hours, minutes, seconds)

@rmaddy's solution is accurate and answers the question. However, neither the question nor the solution take into account international users. I suggest using DateComponentsFormatter and let the framework handle the calculations and formatting. Doing so makes your code less error prone and more future proof.

I came across this blog post that provides a concise solution: http://crunchybagel.com/formatting-a-duration-with-nsdatecomponentsformatter/

Pulled from that post, this is the code snippet that would replace the code you're currently using to make your calculations. Updated for Swift 3:

let duration: TimeInterval = 7200.0

let formatter = DateComponentsFormatter()
formatter.unitsStyle = .positional // Use the appropriate positioning for the current locale
formatter.allowedUnits = [ .hour, .minute, .second ] // Units to display in the formatted string
formatter.zeroFormattingBehavior = [ .pad ] // Pad with zeroes where appropriate for the locale

let formattedDuration = formatter.string(from: duration) 

Swift5

var totalHour = Int()
var totalMinut = Int()
var totalSecond = Int()
var timer:Timer?

call startTimer() based on requirement-

func startTimer(){
timer = Timer.scheduledTimer(timeInterval: 1, target: self, selector: #selector(countdown), userInfo: nil, repeats: true)
}

@objc func countdown() {
    var hours: Int
    var minutes: Int
    var seconds: Int

    if totalSecond == 0 {
        timer?.invalidate()
    }
    totalSecond = totalSecond - 1
    hours = totalSecond / 3600
    minutes = (totalSecond % 3600) / 60
    seconds = (totalSecond % 3600) % 60
    timeLabel.text = String(format: "%02d:%02d:%02d", hours, minutes, seconds)
}

Done