title: vertical reference line in google timeline visualization
body: <p>Hi I am using google visualization api to draw a timeline chart in my website. It works just fine. But there is one little thing that is bothering me. I want to display a vertical line in the chart area to represent the current date. Please let me know any kind of solutions.</p>
  
  <p>My code:</p>
  
  <pre><code>&lt;script type="text/javascript" src="https://www.google.com/jsapi?autoload={'modules':[{'name':'visualization','version':'1','packages':['timeline']}]}"&gt;&lt;/script&gt;
  
  &lt;script type="text/javascript"&gt;
  google.setOnLoadCallback(drawChart);
  function drawChart() {
  
    var container = document.getElementById('example3.1');
    var chart = new google.visualization.Timeline(container);
  
    var dataTable = new google.visualization.DataTable();
    dataTable.addColumn({ type: 'string', id: 'Position' });
    dataTable.addColumn({ type: 'string', id: 'Name' });
    dataTable.addColumn({ type: 'date', id: 'Start' });
    dataTable.addColumn({ type: 'date', id: 'End' });
    dataTable.addRows([
      [ 'President',          'George Washington', new Date(2014, 3, 29), new Date(2014, 4, 3)],
      [ 'President',          'John Adams',        new Date(2014, 2, 3),  new Date(2014, 3, 3)],
      [ 'President',          'Thomas Jefferson',  new Date(2014, 2, 3),  new Date(2014, 5, 3)],
      [ 'Vice President',     'John Adams',        new Date(2014, 3, 20), new Date(2014, 5, 3)],
      [ 'Vice President',     'Thomas Jefferson',  new Date(2014, 2, 3),  new Date(2014, 6, 3)],
      [ 'Vice President',     'Aaron Burr',        new Date(2014, 2, 3),  new Date(2014, 2, 3)],
      [ 'Vice President',     'George Clinton',    new Date(2014, 2, 3),  new Date(2014, 2, 19)],
  
      ]);
  
    chart.draw(dataTable);
  }
  
  &lt;/script&gt;
  
  &lt;div id="example3.1" style="width: 1000px; height: 200px;"&gt;&lt;/div&gt;
  </code></pre>
  
  <p>Intended Result: Green Line represents current date
  <img src="https://i.stack.imgur.com/aLupk.jpg" alt="enter image description here"></p>
  
  <p>Edit:</p>
  
  <p>If this is not possible, please suggest any other API which can achieve this.</p>