title: Chart.js stepSize is not working for Line chart for date
body: <p>I'm plotting a line with <a href="http://www.chartjs.org/" rel="nofollow noreferrer">Chart.js</a>. I'm plotting time against some value. I want fix time slots on axis. I'm using the <code>stepSize</code> property, but it is not applying.</p>
  
  <p>Here is the code:</p>
  
  <pre><code>var data = {
    labels: [1495015201000, 1495015202000, 1495015203000, 1495015204000, 1495015205000, 1495015206000, 1495015207000, 1495015208000, 1495015209000, 1495015210000, 1495015211000, 1495015212000, 1495015213000, 1495015214000, 1495015215000, 1495015216000, 1495015217000, 1495015218000, 1495015219000, 1495015220000, 1495015221000, 1495015222000, 1495015223000, 1495015224000, 1495015225000, 1495015226000, 1495015227000, 1495015228000, 1495015229000, 1495015230000, 1495015231000, 1495015232000, 1495015233000, 1495015234000, 1495015235000, 1495015236000, 1495015237000, 1495015238000, 1495015239000, 1495015240000, 1495015241000, 1495015242000, 1495015243000, 1495015244000, 1495015245000, 1495015246000, 1495015247000, 1495015248000, 1495015249000, 1495015250000, 1495015251000, 1495015252000, 1495015253000, 1495015254000, 1495015255000, 1495015256000, 1495015257000, 1495015258000, 1495015259000, 1495015260000],
    datasets: [{
      label: "DataSet",
      backgroundColor: "rgba(255,99,132,0.2)",
      borderColor: "rgba(255,99,132,1)",
      borderWidth: 1,
      hoverBackgroundColor: "rgba(255,99,132,0.4)",
      hoverBorderColor: "rgba(255,99,132,1)",
      data: [10, 15, 47, 58, 54, 1, 6, 8],
      scaleOverride: false,
      scaleSteps: 0,
      scaleStartValue: 0,
      scaleStepWidth: 1
    }]
  };
  
  var myBarChart = new Chart($("#a"), {
    type: 'line',
    data: data,
    options: {
      scales: {
        yAxes: [{
          scaleLabel: {
            display: true
          }
        }],
        xAxes: [{
          type: 'time',
          autoSkip: false,
          ticks: {
            min: 1495015201000,
            stepSize: 10000,
            max: 1495015260000
          },
          scaleLabel: {
            display: true
          },
        }]
      }
    }
  });
  </code></pre>
  
  <p><a href="https://jsfiddle.net/vishu2111/q7qnh9so/2/" rel="nofollow noreferrer">JSFiddle link</a></p>
  
  <p>I need fix scaling on x-axis based on step size. In current case, I need it with a time difference of 10 seconds. </p>