This is a bug, indeed - it should be fixed now in the latest sandbox build (8.1.1931):
http://javascript.daypilot.org/sandbox/
These indicators are disabled by default - you can enable them using .timeRangeSelectingStartEndEnabled property. It looks like the value is set to true in your project - just remove that setting to disable the indicators.
By the way, you can customize the text/HTML using onTimeRangeSelecting:
dp.onTimeRangeSelecting = function(args) {
args.left.enabled = true;
args.left.html = args.start.toString("d.M.yyyy");
args.right.enabled = true;
args.right.html = args.start.toString("d.M.yyyy");
};
You can also change the default date format directly using .timeRangeSelectingStartEndFormat (without using onTimeRangeSelecting). The default value is "MMMM d, yyyy":
dp.timeRangeSelectingStartEndFormat = "MMMM d, yyyy";