Image Export DayPilot Scheduler

Hello,
I am trying to export DayPilot Scheduler, using this code

setDataSourceAndBind();
DayPilotScheduler1.CssOnly = false;
Response.Clear();
Response.ContentType = "image/png";
Response.AddHeader("content-disposition", "attachment;filename=print.png");
DayPilotScheduler1.DataBind();
MemoryStream img = DayPilotScheduler1.Export(ImageFormat.Png);
img.WriteTo(Response.OutputStream);
DayPilotScheduler1.CssOnly = true;
Response.End();

and the dates in the exported file dont cover all period from DayPilotScheduler1.StartDate to DayPilotScheduler1.EndDate, but only the dates i see on the screen, like printscreen. What can cause this problem?

Thanks in advance,
all comments are very welcome