Find all unique values in array and than split it and return something else

My goal is to find all the unique years in this array and than return it as a array. I have almost done it but cant figure out how I will return the split value.

function findUniqueYears() {
  const arr = ['1973-11-01', '2001-01-01', '1999-10-01', '2007-10-01', '2016-06-01', '2005-08-01', '1973-09-01', '1979-12-01', '2001-08-01'];
  for (var i = 0; i < arr.length; i++) {
    for (var j = i + 1; j < arr.length; j++) {
      if (arr[i].split("-")[0] === arr[j].split("-")[0]) {
        arr.splice(j, 1);
      }
    }
  }
  console.log(arr)
}

>Solution :

This should do

const findUniqueYears = (arr) => Array.from(new Set(arr.map(item => item.split('-')[0])))