Which is the best way to repeat a code every 12 hours in swift for Mac OSX application

Below are the two ways i am doing it, but wanted to know which is best way to do it and why

First way

Timer.scheduledTimer(withTimeInterval: 43200, repeats: true) { timer in
            let randomNumber = Int.random(in: 1...20)
            print("Number: \(randomNumber)")

            if randomNumber == 20 {
                timer.invalidate()
            }
        }

second way

let date = Date().addingTimeInterval(43200)
        let timer = Timer(fireAt: date, interval: 0, target: self, selector: #selector(runCode), userInfo: nil, repeats: false)
        RunLoop.main.add(timer, forMode: .common)
@objc func runCode()
           {
               print("Running code after every 5 seconds")
           }