update DateTimePicker

int d = 1;
int year_int = Convert.ToInt32(year);
int month_int = Convert.ToInt32(month);
start_dTPicker1.Format = DateTimePickerFormat.Custom;

start_dTPicker1.CustomFormat = "yyyy MM dd";
start_dTPicker1.MinDate = new DateTime(year_int,month_int,d);

im trying to add this d,year_int,month_int integer types to dateTimePicker but it doesnt update, please help me

if d=1 , month_int=05, year_int=2012 dateTimePicker value should be updated as 2012/05/1