Using DateFormatter on a Unix timestamp

You can convert unixTimestamp to date using Date(timeIntervalSince1970:).

let unixTimestamp = 1480134638.0
let date = Date(timeIntervalSince1970: unixTimestamp)

If you want to display date in string with specific formate than you can use DateFormatter like this way.

let date = Date(timeIntervalSince1970: unixtimeInterval)
let dateFormatter = DateFormatter()
dateFormatter.timeZone = TimeZone(abbreviation: "GMT") //Set timezone that you want
dateFormatter.locale = NSLocale.current
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm" //Specify your format that you want
let strDate = dateFormatter.string(from: date)

Swift 4.1. I created a function. Just pass you timeStamp in function param and function will return data in string data type. You can add more properties to DateFormatter object.

func getDateFromTimeStamp(timeStamp : Double) -> String {

        let date = NSDate(timeIntervalSince1970: timeStamp / 1000)
        
        let dayTimePeriodFormatter = DateFormatter()
        dayTimePeriodFormatter.dateFormat = "dd MMM YY, hh:mm a"
     // UnComment below to get only time
    //  dayTimePeriodFormatter.dateFormat = "hh:mm a"  

        let dateString = dayTimePeriodFormatter.string(from: date as Date)
        return dateString
    }

The problem is the line dateFormatter.timeZone = NSTimeZone() as TimeZone!.

Simply use TimeZone instead of NSTimeZone like
dateFormatter.timeZone = TimeZone.current and your code will work.

You might also remove your / 1000 because 1480134638.0 looks more like seconds than milliseconds (since 1970).