How to get date label of line Chart?

I use line of Chart.js( Version: 2.7.2 ) in my application and I open dialog when clicking on some element and I need to get label(date on xAxes) of the current element. Googling I found examples and trying to make as next :

        var lineCanvas = document.getElementById("canvasVotesByDays");
        var ctx = lineCanvas.getContext('2d');

        var lineChart = new Chart(ctx, {
            type: 'line',
            data: {
                labels: monthsXCoordItems,
                datasets: [
                    {
                        label: 'Correct Votes',
                ...

        lineCanvas.onclick = function (e) {
            console.log("INSIDE lineChart::")
            console.log(lineChart)

            var slice = lineChart.getPointsAtEvent(e);
            ...

But on the last line I got error :

Uncaught TypeError: lineChart.getPointsAtEvent is not a function
    at HTMLCanvasElement.lineCanvas.onclick 

In the console I see the propeerties of the lineChart object: https://imgur.com/a/E7jsoBc

Why error and how to get label property?

Thank you!

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