You can use DateTime.Today as DayPilotScheduler.StartDate. This will display today as the first day in the matrix.

If you want to show a full week and just set the initial scroll position to today, use the following:

    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            DayPilotScheduler1.SetScrollX(DateTime.Today);
        }
    }