The onBeforeCornerRender event is called during update() and it lets you customize the content of the upper-left corner of the Gantt chart component.
Available since 2020.2.4376.
DayPilot.Gantt.onBeforeCornerRender(args)
dp.onBeforeCornerRender = function(args) {
// display the current year
args.html = dp.visibleStart().toString("yyyy");
};