我也是在网上找的，自己随便改了一下
六个lineEdit控件，每个控件输入日期时间，点击按钮触发函数可修改时间。

 1     //一键修改系统时间

     QString year = ui->lineEdit_9->text();  //年

     QString month = ui->lineEdit_10->text(); //月

     QString day = ui->lineEdit_11->text(); //日

     QString hour = ui->lineEdit_12->text(); //时

     QString min = ui->lineEdit_13->text(); //分

     QString second = ui->lineEdit_14->text(); //秒

     QString a = "date -s" + year + "/" + month + "/" + day;

     QString b = "date -s" + hour + ":" + min + ":" + second;

     char *ch;

     QByteArray ba = a.toLatin1();

     ch = ba.data();

     char *ch_2;

     QByteArray ba_2 = b.toLatin1();

     ch_2 = ba_2.data();

     system(ch);

     system(ch_2);

     //强制写入到CMOS

     system("hwclock -w");