JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://www.chartjs.org/assets/Chart.js"></script>
<canvas id="LineWithLine" width="650" height="400"></canvas>

JavaScript

var data = {
    labels: ["-2h", "-10m", "-7m", "-2m", "-5s"],
    datasets: [{
        data: [12.5, 3.1, 2.3, 1.2, 8.5],
        fillColor: "rgba(151,187,205,0.2)",
        strokeColor: "rgba(151,187,205,1)",
        pointColor: "rgba(151,187,205,1)",
        pointStrokeColor: "#fff",
        pointHighlightFill: "#fff",
        pointHighlightStroke: "rgba(151,187,205,1)",
    }, {
        data: [12.5, 4.1, 3.3, 4.2, 15.5],
        fillColor: "rgba(220,220,220,0.2)",
        strokeColor: "rgba(220,220,220,1)",
        pointColor: "rgba(220,220,220,1)",
        pointStrokeColor: "#fff",
        pointHighlightFill: "#fff",
        pointHighlightStroke: "rgba(220,220,220,1)",
    },

    ]
};

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

Chart.types.Line.extend({
    name: "LineWithLine",
    draw: function () {
        var scale = this.scale;
        var self = this;
        var points = this.options.lineAtIndex

        Chart.types.Line.prototype.draw.apply(this, arguments);

        points.forEach(function (point) {
            var point = self.datasets[0].points[point];
			

            // draw line
            self.chart.ctx.beginPath();
            self.chart.ctx.moveTo(point.x, scale.startPoint + 20);
            self.chart.ctx.strokeStyle = '#ff0000';
            self.chart.ctx.lineTo(point.x, scale.endPoint);
            self.chart.ctx.stroke();

            // write TODAY
            self.chart.ctx.textAlign = 'center';
            self.chart.ctx.fillText("Event", point.x, scale.startPoint + 12);
        });

    }
});

var options = {
   // tooltipTemplate: "<%= value %>",

    showTooltips: true,

   onAnimationComplete: function () {
       var ctx = document.getElementById("LineWithLine").getContext("2d");
       ctx.font = '.8rem "Gotham Book",sans-serif';
				ctx.fontWeight = 'bold';
				ctx.fillStyle = '#000';
				ctx.textAlign="right";
       		var self =...