.valueAsDate返回.value前一天的输入类型日期

Question

有谁知道为什么在输入中提供的日期之前使用.valueAsDate返回？

var result = function(){
  var date = document.getElementById('result').value;
  var dateAsDate = document.getElementById('result').valueAsDate;
  document.getElementById('date').innerHTML = date;
  document.getElementById('dateAsDate').innerHTML = dateAsDate;
}

<input id = 'result' type = date>
<button onclick = 'result();'>Result</button>
<div id = 'date'></div>
<div id = 'dateAsDate'></div>