how to edit TimescaleStart of MS Project Using C#.net

I have a requirement to modify the ms project file (.mpp) using C#.net.

I have done with all the things, the only thing remaining is to modify the TimescaleStart date of MPP file using C#.net. I need to set the user defined date.

How can i do that?

Following is my code:

Microsoft.Office.Interop.MSProject.Application app = new Microsoft.Office.Interop.MSProject.Application();
app.DisplayAlerts = false;
app.AskToUpdateLinks = false;


app.FileOpenEx(
strFilePath + "test.mpp",
false,
Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing,
PjPoolOpen.pjPoolReadWrite, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

Microsoft.Office.Interop.MSProject.Project pj = app.ActiveProject;

object objDate = dt.Date;
app.TimescaleStart =   objDate;

Got Error as

Type mismatch. (Exception from HRESULT: 0x80020005 (DISP_E_TYPEMISMATCH))

on Following line:

app.TimescaleStart =   objDate;

TimescaleStart is a read-only property which returns the date that the timescale starts in the current view.

If you want to scroll the view so that it starts at a certain date, find a task with a start date on or close to your target date, select it and invoke the GotoTaskDates method of the application object. For example:

 app.Find "Start", "is greater than or equal to", "1/1/2014", Type.Missing, Type.Missing, Type.Missing, Type.Missing
 app.GotoTaskDates

Update:

If you are using Project 2010 or later, you can also use this method:

app.PanZoomPanTo (objDate)