jquery unix time, timestamp узнать прошла ли минута

вот так преобразуйте

const time = localStorage.getItem('user-online-timestamp');
let localStorageTime = new Date(+time);

а скрипт будет примерно такой

const timestamp = new Date().getTime();
if (localStorage.getItem('user-online-timestamp') == undefined) {
    localStorage.setItem('user-online-timestamp', timestamp);
}
localStorageTime();
setTimeout( localStorageTime, 60000);
function localStorageTime()
{
    const timeStamp = new Date().getTime();
    const time = localStorage.getItem('user-online-timestamp');
    let localStorageTime = new Date(+time);
    if (timeStamp - localStorageTime >= 60000) {
        console.log("минута прошла");
    } else {
        console.log("минута не прошла");
    }
    console.log(timeStamp - localStorageTime);
}