Code

c.CustomDraw = CustomDrawElements.TimetableCell | CustomDrawElements.TimetableTimelineCell;
c.Draw += (s, e) =>
	{
		if (e.Element == CustomDrawElements.TimetableCell)
		{
			if (e.Date + e.StartTime <= DateTime.Now && DateTime.Now <= e.Date + e.EndTime)
			{
				long ticks = DateTime.Now.Ticks - (e.Date + e.StartTime).Ticks;
				long total = (e.EndTime - e.StartTime).Ticks;
				var h = e.Bounds.Height * ticks / total;
				using (var pen = new Pen(Color.Red, 4))
					e.Graphics.DrawLine(pen, e.Bounds.X, e.Bounds.Y + h, e.Bounds.Right, e.Bounds.Y + h);
			}
		}
		if (e.Element == CustomDrawElements.TimetableTimelineCell)
		{
			if (e.StartTime <= DateTime.Now.TimeOfDay && DateTime.Now.TimeOfDay <= e.EndTime)
			{
				long ticks = DateTime.Now.TimeOfDay.Ticks - (e.Date + e.StartTime).Ticks;
				long total = (e.EndTime - e.StartTime).Ticks;
				var h = e.Bounds.Height * ticks / total;
				using (var pen = new Pen(Color.Red, 4))
					e.Graphics.DrawLine(pen, e.Bounds.X, e.Bounds.Y + h, e.Bounds.Right, e.Bounds.Y + h);
			}
		}
	}; 

Code

c.Paint += (s, e) =>
	{
		var bounds = c.GetElementBounds(CalendarElement.TimetableDayHeader, 0);
		var firstVisibleTime = new TimeSpan(c.VScrollPos * c.TimetableSettings.CellTime.Ticks);
		if (DateTime.Now.TimeOfDay > firstVisibleTime)
		{
			float dcell = (float)(DateTime.Now.TimeOfDay.Ticks - firstVisibleTime.Ticks) / c.TimetableSettings.CellTime.Ticks;
			var y = bounds.Bottom + dcell * c.TimetableSettings.CellSize;
			using (var pen = new Pen(Color.Red, 4))
				e.Graphics.DrawLine(pen, 0, y, Width, y);
		}
	}; 

Code

c.TimetableSettings.StartTime = 60 * 8; // specified in minutes
 

Code

var firstVisibleTime =
	new TimeSpan(c.VScrollPos * c.TimetableSettings.CellTime.Ticks) +
	TimeSpan.FromMinutes(c.TimetableSettings.StartTime);