Conversion from NSTimeInterval to hour,minutes,seconds,milliseconds in swift - From http://stackoverflow.com/questions/28872450/conversion-from-nstimeinterval-to-hour-minutes-seconds-milliseconds-in-swift
func stringFromTimeInterval(interval: TimeInterval) -> NSString {
let ti = NSInteger(interval)
let ms = Int((interval % 1) * 1000)
let seconds = ti % 60
let minutes = (ti / 60) % 60
let hours = (ti / 3600)
return NSString(format: "%0.2d:%0.2d:%0.2d.%0.3d",hours,minutes,seconds,ms)
}