dynamically set background

Yes, you can use BeforeEventRender event to customize the event appearance:

protected void DayPilotScheduler1_BeforeEventRender(object sender, BeforeEventRenderEventArgs e)
{
  if (e.Start < DateTime.Now) {
    e.BackgroundColor = "#cccccc";
  }
}

See also:
https://doc.daypilot.org/scheduler/event-customization/

Dan,
thank you for your reply. I probably mixed up terminology. What i meant is not actually event itself but rather entire background of calendar.

You can also change the background color of the grid cells, the mechanism is the same. Just use BeforeCellRender event handler:

protected void DayPilotScheduler1_BeforeCellRender(object sender, DayPilot.Web.Ui.Events.BeforeCellRenderEventArgs e)
{
  if (e.Start < DateTime.Now) {
    e.BackgroundColor = "#cccccc";
  }
}

See also:
https://doc.daypilot.org/scheduler/cell-customization/

Hi Dan,
I have a problem with the background color of the event. I have set it in the same way as above in the Before Event Render but when i do an Event Move i need to change the background color again. I am able to update the Scheduler event but the color doesn't change because the Before Event Render event doesn't fire again. How can i fire the event again when i execute Event Move?