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<!DOCTYPE html>
<html>
<body>
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<p>单击该按钮可显示指定日期与 1970 年 1 月 1 日之间的年数。</p>
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<button onclick="myFunction()">试一试</button>
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<p id="demo"></p>
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<script>
function myFunction() {
  var d = Date.parse("March 21, 2012");
  var minutes = 1000 * 60;
  var hours = minutes * 60;
  var days = hours * 24;
  var years = days * 365;
  var y = Math.round(d / years);
​
  document.getElementById("demo").innerHTML = y;
}
</script>
​
</body>
</html>
​