public void ChangeStart()
{
var first = new DateRange(this.date1900, this.date2000);
Assert.AreEqual(new DateRange(this.date1950, this.date2000), first.ChangeStart(this.date1950), "ChangeStart Date");
Assert.AreEqual(new DateRange(this.date1900.AddDays(-1), this.date2000), first.ChangeStart(new TimeSpan(-1, 0, 0, 0)), "ChangeStart TimeSpan");
}