I have an issue with this piece of code it doesn't seem to work what I am doing wrong?

DepartureDate = DatePicked

```
DateTime today = DateTime.Today;
DateTime seven = DateTime.Today.AddDays(+7);
DateTime dt = Convert.ToDateTime(DepartureDate);

if (columnName == "DepartureDate")
{
    //range between today and seven days ahead +7
    if (dt >= today || dt <= seven)
    {
        result = valid;
        return result;
    }
    //can't be in the past
    if (dt < today)
    {
        result = "Can't be in the past";
        return result;
    }
}

```