iOS Swift : Compute mins and seconds from TimeInterval

Here is the logic

let diff : TimeInterval = Date().timeIntervalSince1970 - capturedStartTimeSecs
let remaining : TimeInterval = capturedStartTimeSecs - diff;
let minutes : TimeInterval = remaining  / 60;
var mins : String = String(Int(minutes)) + "";
if(Int(minutes) < 10){
      mins = "0" + String(Int(minutes));
}
               
var seconds = remaining
seconds.formTruncatingRemainder(dividingBy:60) ;
var secs : String = String(Int(seconds)) + "";
if(Int(seconds) < 10){
      secs = "0" + String(Int(seconds))
}