title: jq dates and unix timestamps
body: <p>So I have a data with bunch of unix timestamp values (in milliseconds). Something like this:</p>
  
  <pre><code>{
      "id": "f6922fd5-4f97-4113-820e-b45eba0ae236",
      "published_at": 1461624333859,
      "tracking_id": "a85d5ed5-5efa-461b-aae0-beb2098c0ff7",
  }, {
      "id": "835d412f-5162-440c-937b-7276f22c4eb9",
      "published_at": 1461625249934,
      "tracking_id": "86472ba2-ce5f-400f-b42a-5a0ac155c42c",
  }, {
      "id": "bc2efcac-67a0-4855-856a-f31ce5e4618e",
      "published_at": 1461625253393,
      "tracking_id": "c005398f-07f8-4a37-b96d-9ab019d586c2",
  }
  </code></pre>
  
  <p>And very often we need to search for rows within a certain date. Is it possible to query with jq, providing human readable dates e.g. <code>2016-04-25</code>. Also I wonder if the other way around possible, to make jq show <code>published_at</code> values in human readable form? </p>
  
  <p>For example this works:</p>
  
  <pre><code>$ echo 1461624333 | jq 'todate'   
  "2016-04-25T22:45:33Z"
  </code></pre>
  
  <p>although it has to be in seconds, not milliseconds</p>