C++ 获取所有星期日的日期

timer tm;
 date dtStartDate = from_undelimited_string("20080116");
 date dtEndDate = from_undelimited_string("20130120");  
 date tem ;
 int count = 0;
 int gap = 0;
 if (dtStartDate > dtEndDate)
 {
  return ;
 }
 if (dtStartDate.day_of_week() == 0)
 {
  tem = dtStartDate;
 }
 else
 {
  gap = dtStartDate.day_of_week();
  tem = dtStartDate - days(gap);
 }

 for (; tem <= dtEndDate ; tem += days(7) )
 {
  ++count;
  //cout << to_iso_string( tem) << " 星期" << tem.day_of_week() << endl;
 }

 cout << "总共" << count << "个星期" << endl;
 double duration = tm.elapsed();
 cout << "总共耗时:" << duration << endl;