Schlagwort: getUTCFullYear

function getAge(oDate)
{
    let diff_ms = Date.now() - oDate.getTime();
    let age_ms = new Date(diff_ms);
    let age_years = age_ms.getUTCFullYear() - 1970;
    return age_years < 0 ? NaN : age_years;
}

let oBirthDay = new Date(2000, 1, 1);
console.log(getAge(oBirthDay));