clock.js

setInterval(setClock, 1000)

const hourhand = document.querySelector('[data-hour-hand]');
const minutehand = document.querySelector('[data-minute-hand]');
const secondshand = document.querySelector('[data-seconds-hand]');

function setClock()
{
    const currentDate = new Date();
    const secondsRatio = currentDate.getSeconds() / 60;
    const minutesRatio = (secondsRatio + currentDate.getMinutes()) / 60;
    const hoursRatio = (minutesRatio + currentDate.getHours()) / 12;

    setRotation(secondshand, secondsRatio);
    setRotation(minutehand, minutesRatio);
    setRotation(hourhand, hoursRatio);
}

function setRotation(element, rotationRatio)
{
    element.style.setProperty('--rotation', rotationRatio * 360);
}

setClock();