1、必須加標頭檔案 #include <cstdlib>
2、程式碼：
date.cpp
void Date::setDate(QString year, QString month, QString day, QString hour, QString minute, QString second)
{
    QString str= "date -s " + year + month + day + hour + minute + "." + second;
    system(str.toLatin1().data());
    //強制寫入到CMOS
    system("hwclock -w");
}
date.h
class Date : public QObject
{
    Q_OBJECT
public slots:
    void setDate(QString year, QString month, QString day, QString hour, QString minute, QString second);
};