@gbienemannkahle-schule-de,
You can use the indexLabelFormatter function to display custom index labels as per your requirement. Please take a look at the code-snippet given below.
indexLabelFormatter: function(e) {
var s = e.dataPoint.y % 1; s *= 60;
var m = e.dataPoint.y % 60;
var h = (e.dataPoint.y - m) / 60;
return (h < 10 ? "0" : "") + h.toString() + ":" + (m < 10 ? "0" : "") + Math.trunc(m).toString() + ":" + (s < 10 ? "0" : "") + s.toString();
},
—
Thangaraj Raman
Team CanvasJS