SYSTEMTIME 获取日期之差

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ATLComTime.h>
#pragma once 
#pragma warning(disable:4996)

int CompareSystemTime(SYSTEMTIME &stStart, SYSTEMTIME &stEnd)
{//获取两个    SYSTEMTIME的日期之差
    COleDateTime m_tStartDate;
    COleDateTime m_tEndDate;
    m_tStartDate.SetDate(stStart.wYear, stStart.wMonth, stStart.wDay);
    m_tEndDate.SetDate(stEnd.wYear, stEnd.wMonth, stEnd.wDay);
    
    COleDateTimeSpan nDays = m_tEndDate - m_tStartDate;
    return (int)nDays.GetDays();
}

SYSTEMTIME GetDateAdded(SYSTEMTIME &stStart)
{//起始日期增加一天
    COleDateTime m_tStartDate;
    m_tStartDate.SetDate(stStart.wYear, stStart.wMonth, stStart.wDay);

    COleDateTimeSpan ts2(1); 
    m_tStartDate += ts2;
    SYSTEMTIME stTemp;
    stTemp.wYear = m_tStartDate.GetYear();
    stTemp.wMonth = m_tStartDate.GetMonth();
    stTemp.wDay = m_tStartDate.GetDay();
    return stTemp;
}

//主函数
int main(void)
{
    SYSTEMTIME st, st1;
    st.wYear = 2014;
    st.wMonth = 12;
    st.wDay = 31;
    GetLocalTime(&st1);
    
    int nDays = CompareSystemTime(st, st1);
    printf("%d\n", nDays);

    st = GetDateAdded(st);
    printf("%d-%02d-%02d\n", st.wYear, st.wMonth, st.wDay);
    nDays = CompareSystemTime(st, st1);
    printf("%d\n", nDays);
    return 0;
}