Just use two placeholder divs and create a DayPilot.Gantt instance for each of them:
<div id="gantt1"></div>
<div id="gantt2"></div>
<script>
var gantt1 = new DayPilot.Gantt("gantt1");
// config ....
gantt1.init();
var gantt2 = new DayPilot.Gantt("gantt2");
// config ...
gantt2.init();
</script>