Formatting

Format NSTimeInterval as hh:mm

let wholeSeconds = UInt64(elapsed)
let minutes = wholeSeconds / 60
let seconds = wholeSeconds % 60
let formatted = String.localizedStringWithFormat("%02d:%02d", minutes, seconds)

Format NSDate:

let formatter = NSDateFormatter()
formatter.dateStyle = .NoStyle
formatter.timeStyle = .ShortStyle
let formattedTime = formatter.stringFromDate(originalStartTime!)

h/t https://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Classes/NSDateFormatter_Class/index.html#//apple_ref/occ/cl/NSDateFormatter