求输入日期是星期几

/*******************************************************
**
** 功能：求输入日期是星期几 （0表示星期天，其余为 1-6）
** 日期：2006-6-16
**
**
********************************************************/
int CMy33Dlg::SW_WeekDay(int year, int month, int day)
{
int DayOfWeek;
/*下面的四条语句用来计算输入日期的星期数，是程序的核心部分，缺一不可*/
DayOfWeek=year>0 ? (5 + (year+ 1)+(year-1)/4 -(year-1)/100 + (year-1)/400)%7
: (5 + year + year/4 - year/100 + year/400) % 7;
DayOfWeek = month > 2 ? (DayOfWeek + 2*(month + 1) + 3*(month + 1)/5) % 7
: (DayOfWeek + 2*(month + 2) + 3*(month + 2)/5) % 7;
if (((year%4 == 0 && year%100 != 0) || year%400 == 0) && month>2)
{
DayOfWeek = (DayOfWeek + 1) % 7;
}
DayOfWeek = (DayOfWeek + day) % 7;
CString strtemp;
switch(DayOfWeek)
{
case 0:
strtemp="今天是星期日";
break;
case 1:
strtemp="今天是星期一";
break;
case 2:
strtemp="今天是星期二";
break;
case 3:
strtemp="今天是星期三";
break;
case 4:
strtemp="今天是星期四";
break;
case 5:
strtemp="今天是星期五";
break;
case 6:
strtemp="今天是星期六";
break;
default:
strtemp="请你查看年月日是否输入完全！";
break;
}

MessageBox(strtemp);
return DayOfWeek;
}
//功能：调用SW_WeekDay()函数，查看是星期几
void CMy33Dlg::OnbtnWeek()
{
UpdateData();
int year,month,day;
if(m_editStrYear!=""&&m_editStrMonth!=""&&m_editStrDay!="")
{
year=atoi(m_editStrYear); //m_eidtStrYear 为编辑框的变量名
month=atoi(m_editStrMonth);
day=atoi(m_editStrDay);
}
SW_WeekDay(year,month,day); //调用计算星期几的函数
UpdateData(false);
}