C++日期比较大小

date dtStartDate = from_undelimited_string("20130116");
date dtEndDate = from_undelimited_string("20130115");
if (dtStartDate == dtEndDate)
{
cout << "等于" << endl;
}
else if (dtStartDate < dtEndDate)
{
cout << "小于" << endl;
}
else
{
cout << "大于" << endl;
}