My application heavily relies on time calculation and I read online that GCP App Engine uses UTC time zone. So I made these calculations and on my local dev, the calcTime is totally different than App Engine, App Engine is giving me a big -negative number I'm not sure why??

    const endTime = Math.floor(new Date(filteredTimeLeft).getTime() / 1000);
const convertSec = Number(coin.seconds);
const dateNow = Math.floor(Date.now() / 1000);
const calcTime = endTime - convertSec - dateNow;

Isn't my code suppose to work universally , independent where the server is located at?