Please see an example from Demo/Scheduler/Default.aspx.cs:
protected void DayPilotScheduler1_BeforeResHeaderRender(object sender, DayPilot.Web.Ui.Events.BeforeHeaderRenderEventArgs e)
{
if (e.IsCorner)
{
e.InnerHTML = String.Format("<div style='padding:5px; font-weight: bold; font-size:22px; text-align:center'>{0}</div>", DayPilotScheduler1.StartDate.Year);
}
}