Question

what should I do that the time items appear in 3d? I mean to get a color gradient?

Answer

In GTP.NET you can set the TimeItemLayout this way:

ti1.TimeItemLayout=new TimeItemLayout();
ti1.TimeItemLayout.BrushKind=BrushKind.GradientDiagonal;
ti1.TimeItemLayout.Color=Color.YellowGreen;
ti1.TimeItemLayout.GradientColor=Color.Yellow;

In phGantTimePackage you can get a gradient effect doing like this:
time.Style = txTimeStyle.tsPipe;