Chart.js creating a line graph using dates

Question

I can't seem to get Chart.js to work with dates. I have tried quite a few different methods:

let examChart = document.getElementById("examChart").getContext("2d");
let examLineChart = new Chart(examChart, {
    type: "line",
    data: [
            { t: new Date("2015-3-15 13:3"), y: 12 },
            { t: new Date("2015-3-25 13:2"), y: 21 },
            { t: new Date("2015-4-25 14:12"), y: 32 }
    ],
    options: {
        label: "placeholder"
    }
});

And:

let examChart = document.getElementById("examChart").getContext("2d");
let examLineChart = new Chart(examChart, {
    type: "line",
    data: [
            { t: "2015-3-15 13:3", y: 12 },
            { t: "2015-3-25 13:2", y: 21 },
            { t: "2015-4-25 14:12", y: 32 }
    ],
    options: {
        label: "placeholder"    
    }
});

And:

let examChart = document.getElementById("examChart").getContext("2d");
let examLineChart = new Chart(examChart, {
    type: "line",
    data: [
            { t: "Sun Mar 15 2015 12:03:45 GMT+0000 (GMT Standard Time)", y: 12 },
            { t: "Wed Mar 25 2015 12:02:15 GMT+0000 (GMT Standard Time)", y: 21 },
            { t: "Sat Apr 25 2015 13:12:30 GMT+0100 (GMT Daylight Time)", y: 32 }
    ],
    options: {
        label: "placeholder"    
    }
});

To cover just a few of my attempts, I just can't seem to get how to set dates properly even after reading the documentation (http://www.chartjs.org/docs/latest/axes/cartesian/time.html) (they don't actually give an example)

The HTML being used:

<div class="container">
    <canvas id="examChart"></canvas>
</div>

I just have no idea, although I imagine this is a rather simple problem, any help would be greatly appreciated.

Answer 1

You have to move your data within a dataset. If you take a look at the usage manual, a datasets array is used. The "hint" for datasets within the docs for time is also not that obvious (See headline).

See the snippet below:

I just copied the basic usage example and inserted the data from your first attempt (+ added few labels)

UPDATE 18.03.2020

I've updated the snippet to use Chart.js 2.8.0 and added following code, as suggested in the comment by @Erik

options: {
    scales: {
      xAxes: [{
        type: 'time'
      }]
    }
  }

var ctx = document.getElementById("examChart").getContext("2d");

var myChart = new Chart(ctx, {
  type: 'line',
  data: {
    labels: [new Date("2015-3-15 13:3").toLocaleString(), new Date("2015-3-25 13:2").toLocaleString(), new Date("2015-4-25 14:12").toLocaleString()],
    datasets: [{
      label: 'Demo',
      data: [{
          t: new Date("2015-3-15 13:3"),
          y: 12
        },
        {
          t: new Date("2015-3-25 13:2"),
          y: 21
        },
        {
          t: new Date("2015-4-25 14:12"),
          y: 32
        }
      ],
      backgroundColor: [
        'rgba(255, 99, 132, 0.2)',
        'rgba(54, 162, 235, 0.2)',
        'rgba(255, 206, 86, 0.2)',
        'rgba(75, 192, 192, 0.2)',
        'rgba(153, 102, 255, 0.2)',
        'rgba(255, 159, 64, 0.2)'
      ],
      borderColor: [
        'rgba(255,99,132,1)',
        'rgba(54, 162, 235, 1)',
        'rgba(255, 206, 86, 1)',
        'rgba(75, 192, 192, 1)',
        'rgba(153, 102, 255, 1)',
        'rgba(255, 159, 64, 1)'
      ],
      borderWidth: 1
    }]
  },
  options: {
    scales: {
      xAxes: [{
        type: 'time'
      }]
    }
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.8.0/Chart.bundle.js"></script>
<div class="container">
  <canvas id="examChart"></canvas>
</div>