the DateTimePicker can show only one calender at a time. But if you want to show two calenders at a time, then you can dynamically adding another monthcalender when the datetimepicker is dropped down.
MonthCalender cln= new MonthCalender();
private void DateTimePicker1_DropDown(object sender,
System.EventArgs e)
{
cln.now.AddDays(30);
cln.location = new point(x,y);
this.controls.Add(cln);;
private void DateTimePicker1_CloseUp(Object sender, EventArgs e)
{
cln.Hide();
}