function startDateTimeDisplay() {

    const displayNode = document.querySelector('#datetime span')
    let dateTime = new Date()

    const updateDateTime = () => {
        displayNode.innerHTML = dateTime.toString()
        dateTime = new Date()
        window.requestAnimationFrame(updateDateTime)
    }

    window.requestAnimationFrame(updateDateTime)
}

window.onload = () => {
    startDateTimeDisplay()
}