從源碼可知以下按鈕的名稱，
//set names for the header controls.
//prevMonth->setObjectName(QLatin1String("qt_calendar_prevmonth"));
//nextMonth->setObjectName(QLatin1String("qt_calendar_nextmonth"));
//monthButton->setObjectName(QLatin1String("qt_calendar_monthbutton"));
//yearButton->setObjectName(QLatin1String("qt_calendar_yearbutton"));
//yearEdit->setObjectName(QLatin1String("qt_calendar_yearedit"));
你可以獲取到QToolButton的對象，你想咋整都行。
QToolButton *tools = calendar->findChild<QToolButton*>(QLatin1String("qt_calendar_prevmonth"));