date = new Date('2021-09-16T10:20:00.000Z');
year = date.getFullYear();
month = date.getMonth()+1;
dt = date.getDate();

if (dt < 10) {
  dt = '0' + dt;
}
if (month < 10) {
  month = '0' + month;
}

console.log(year+'-' + month + '-'+dt);