title: Get max and min dates from an array
body: <p>I have sample data as:</p>
  
  <pre><code>data = [
    [1, 622, 782, 783, "2015-04-21"],
    [2, 622, 782, 783, "2015-04-21"],
    [3, 622, 782, 783, "2015-04-22"],
    [4, 622, 782, 783, "2015-04-23"],
    [5, 622, 782, 783, "2015-04-24"],
    [6, 622, 782, 783, "2015-04-28"],
    [7, 622, 782, 783, "2015-04-28"],
    [8, 622, 782, 783, "2015-04-29"],
    [9, 622, 782, 783, "2015-05-04"],
    [10, 622, 782, 783, "2015-05-05"]
  ]
  </code></pre>
  
  <p>How can I get the max date value and min date value from the above data? The data may be not in sorted order.</p>