calendar.cpp

#include "calendar.h"

Calendar::Calendar(QWidget *parent) :
    QWidget(parent)
{
    qCal = new QCalendarWidget;
    qBtn = new QPushButton(tr("Press me"));

    connect(qBtn, SIGNAL(clicked()), this, SLOT(testCustomClick()));

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(qCal);
    layout->addWidget(qBtn);

    setLayout(layout);
    qDebug() << "Date:" << QDate::currentDate();
}

Calendar::~Calendar()
{
}

void Calendar::testCustomClick()
{
    QMouseEvent qm2(QEvent::MouseButtonPress, QPoint(qCal->width()/2,qCal->height()/2), Qt::LeftButton , Qt::LeftButton, Qt::NoModifier);
    QApplication::sendEvent(qCal, &qm2);
    qDebug() << "isAccepted: " << qm2.isAccepted(); //prints False
}

void Calendar::mousePressEvent(QMouseEvent* ev)
{
    qDebug() << "mouse event: " << ev << "x=" << ev->x() <<" y=" << ev->y();
    QWidget::mousePressEvent(ev);
}

calendar.h

#ifndef CALENDAR_H
#define CALENDAR_H

#include <QtGui>

class Calendar : public QWidget
{
    Q_OBJECT

public:
    explicit Calendar(QWidget *parent = 0);
    ~Calendar();

private slots:
    void testCustomClick();

private:
    QCalendarWidget *qCal;
    QPushButton *qBtn;

protected:
    virtual void mousePressEvent(QMouseEvent *);

};

#endif // CALENDAR_H

main.cpp

#include <QtGui/QApplication>

#include "calendar.h"

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    Calendar cal;
    cal.show();

    return a.exec();
}