Create a constructor on form2 with input parameter as date time. And when you create object of form2 in form1 just pass the date value using C# in window application.
form1 coding:
DateTime objdate = dateTimePicker1.Value;
form2 objform2= new form2(objdate)
objform2.show();
Form2 coding:
DateTime dateen;
// Constructor
public form2(DateTime str)
{
dateen = str;
}