Customise Cell Duration Label

This is a duplication of another question,

http://forums.daypilot.org/Topic.aspx/3082/month-view-split-day-morning-afternoon

You can customize the time headers using OnBeforeTimeHeaderRender:
http://doc.daypilot.org/scheduler/time-header-customization/

The sample code would look like this:

protected override void OnBeforeTimeHeaderRender(BeforeTimeHeaderRenderArgs e)
{
  if (e.Level == 1) {  // second time header row
    if (e.Start.Hour == 0) {
      e.InnerHtml = "Morning";
    }
    else {
      e.InnerHtml = "Afternoon";
    }
  }
}

Just one more note - you will probably want to use CellDuration = 720 (1440 would be one day).