title: getting TypeError: can only concatenate tuple (not "str") to tuple with creating datetime
body: <p>I need to convert a date 2017-12-03 to the format 2017-12-03T00:00.000Z but am running into the error:</p>
  <pre><code>    TypeError: can only concatenate tuple (not &quot;str&quot;) to tuple
  </code></pre>
  <p>I am concatenating like this:</p>
  <pre><code>    start_date_formatted = start_date + &quot;T00:00.000Z&quot;
  </code></pre>
  <p>The start_date is a tuple. If I print it out it appears in the terminal as ('2017-12-03,',)</p>
  <p>I tried using</p>
  <pre><code>    from ast import literal_eval as make_tuple
  </code></pre>
  <p>but this creates another error.</p>
  <p>What is the correct way to concatenate to format the date?</p>