Adapt QCalendarWidget and QDateTimeEdit to support choice of calendar

[ChangeLog][QtWidgets][QCalendarWidget] Allow choice of calendar, with
Gregorian remaining the default.

[ChangeLog][QtWidgets][QDateTimeEdit] Allow choice of calendar, with
Gregorian remaining the default.

Change-Id: Ia11dd895032393543aee534b177324e643dcfb20
Done-with: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 198 insertions, 135 deletions

diff --git a/src/widgets/widgets/qcalendarwidget.cpp b/src/widgets/widgets/qcalendarwidget.cpp
index 81cc0b833a..296a15f94b 100644
--- a/src/widgets/widgets/qcalendarwidget.cpp
+++ b/src/widgets/widgets/qcalendarwidget.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2016 The Qt Company Ltd.
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtWidgets module of the Qt Toolkit.
@@ -57,6 +57,7 @@
 #include <private/qapplication_p.h>
 #include <qbasictimer.h>
 #include <qstylepainter.h>
+#include <qcalendar.h>
 
 #include <vector>
 
@@ -90,16 +91,15 @@ public:
     QCalendarDateSectionValidator() {}
     virtual ~QCalendarDateSectionValidator() {}
     virtual Section handleKey(int key) = 0;
-    virtual QDate applyToDate(const QDate &date) const = 0;
-    virtual void setDate(const QDate &date) = 0;
+    virtual QDate applyToDate(const QDate &date, QCalendar cal = QCalendar()) const = 0;
+    virtual void setDate(const QDate &date, QCalendar cal = QCalendar()) = 0;
     virtual QString text() const = 0;
-    virtual QString text(const QDate &date, int repeat) const = 0;
+    virtual QString text(const QDate &date, QCalendar cal, int repeat) const = 0;
 
     QLocale m_locale;
 
 protected:
     static QString highlightString(const QString &str, int pos);
-private:
 };
 
 QString QCalendarDateSectionValidator::highlightString(const QString &str, int pos)
@@ -117,10 +117,10 @@ class QCalendarDayValidator : public QCalendarDateSectionValidator
 public:
     QCalendarDayValidator();
     virtual Section handleKey(int key) override;
-    virtual QDate applyToDate(const QDate &date) const override;
-    virtual void setDate(const QDate &date) override;
+    virtual QDate applyToDate(const QDate &date, QCalendar cal) const override;
+    virtual void setDate(const QDate &date, QCalendar cal) override;
     virtual QString text() const override;
-    virtual QString text(const QDate &date, int repeat) const override;
+    virtual QString text(const QDate &date, QCalendar cal, int repeat) const override;
 private:
     int m_pos;
     int m_day;
@@ -181,21 +181,18 @@ QCalendarDateSectionValidator::Section QCalendarDayValidator::handleKey(int key)
     return QCalendarDateSectionValidator::ThisSection;
 }
 
-QDate QCalendarDayValidator::applyToDate(const QDate &date) const
+QDate QCalendarDayValidator::applyToDate(const QDate &date, QCalendar cal) const
 {
-    int day = m_day;
-    if (day < 1)
-        day = 1;
-    else if (day > 31)
-        day = 31;
-    if (day > date.daysInMonth())
-        day = date.daysInMonth();
-    return QDate(date.year(), date.month(), day);
+    auto parts = cal.partsFromDate(date);
+    if (!parts.isValid())
+        return QDate();
+    parts.day = qMin(qMax(1, m_day), cal.daysInMonth(parts.year, parts.month));
+    return cal.dateFromParts(parts);
 }
 
-void QCalendarDayValidator::setDate(const QDate &date)
+void QCalendarDayValidator::setDate(const QDate &date, QCalendar cal)
 {
-    m_day = m_oldDay = date.day();
+    m_day = m_oldDay = date.day(cal);
     m_pos = 0;
 }
 
@@ -204,16 +201,16 @@ QString QCalendarDayValidator::text() const
     return highlightString(formatNumber(m_day, 2), m_pos);
 }
 
-QString QCalendarDayValidator::text(const QDate &date, int repeat) const
+QString QCalendarDayValidator::text(const QDate &date, QCalendar cal, int repeat) const
 {
     if (repeat <= 1) {
-        return QString::number(date.day());
+        return QString::number(date.day(cal));
     } else if (repeat == 2) {
-        return formatNumber(date.day(), 2);
+        return formatNumber(date.day(cal), 2);
     } else if (repeat == 3) {
-        return m_locale.dayName(date.dayOfWeek(), QLocale::ShortFormat);
+        return m_locale.dayName(date.dayOfWeek(cal), QLocale::ShortFormat);
     } else /* repeat >= 4 */ {
-        return m_locale.dayName(date.dayOfWeek(), QLocale::LongFormat);
+        return m_locale.dayName(date.dayOfWeek(cal), QLocale::LongFormat);
     }
 }
 
@@ -225,10 +222,10 @@ class QCalendarMonthValidator : public QCalendarDateSectionValidator
 public:
     QCalendarMonthValidator();
     virtual Section handleKey(int key) override;
-    virtual QDate applyToDate(const QDate &date) const override;
-    virtual void setDate(const QDate &date) override;
+    virtual QDate applyToDate(const QDate &date, QCalendar cal) const override;
+    virtual void setDate(const QDate &date, QCalendar cal) override;
     virtual QString text() const override;
-    virtual QString text(const QDate &date, int repeat) const override;
+    virtual QString text(const QDate &date, QCalendar cal, int repeat) const override;
 private:
     int m_pos;
     int m_month;
@@ -289,23 +286,19 @@ QCalendarDateSectionValidator::Section QCalendarMonthValidator::handleKey(int ke
     return QCalendarDateSectionValidator::ThisSection;
 }
 
-QDate QCalendarMonthValidator::applyToDate(const QDate &date) const
+QDate QCalendarMonthValidator::applyToDate(const QDate &date, QCalendar cal) const
 {
-    int month = m_month;
-    if (month < 1)
-        month = 1;
-    else if (month > 12)
-        month = 12;
-    QDate newDate(date.year(), m_month, 1);
-    int day = date.day();
-    if (day > newDate.daysInMonth())
-        day = newDate.daysInMonth();
-    return QDate(date.year(), month, day);
+    auto parts = cal.partsFromDate(date);
+    if (!parts.isValid())
+        return QDate();
+    parts.month = qMin(qMax(1, m_month), cal.monthsInYear(parts.year));
+    parts.day = qMin(parts.day, cal.daysInMonth(parts.year, m_month)); // m_month or parts.month ?
+    return cal.dateFromParts(parts);
 }
 
-void QCalendarMonthValidator::setDate(const QDate &date)
+void QCalendarMonthValidator::setDate(const QDate &date, QCalendar cal)
 {
-    m_month = m_oldMonth = date.month();
+    m_month = m_oldMonth = date.month(cal);
     m_pos = 0;
 }
 
@@ -314,16 +307,16 @@ QString QCalendarMonthValidator::text() const
     return highlightString(formatNumber(m_month, 2), m_pos);
 }
 
-QString QCalendarMonthValidator::text(const QDate &date, int repeat) const
+QString QCalendarMonthValidator::text(const QDate &date, QCalendar cal, int repeat) const
 {
     if (repeat <= 1) {
-        return QString::number(date.month());
+        return QString::number(date.month(cal));
     } else if (repeat == 2) {
-        return formatNumber(date.month(), 2);
+        return formatNumber(date.month(cal), 2);
     } else if (repeat == 3) {
-        return m_locale.standaloneMonthName(date.month(), QLocale::ShortFormat);
+        return cal.standaloneMonthName(m_locale, date.month(cal), QLocale::ShortFormat);
     } else /*if (repeat >= 4)*/ {
-        return m_locale.standaloneMonthName(date.month(), QLocale::LongFormat);
+        return cal.standaloneMonthName(m_locale, date.month(cal), QLocale::LongFormat);
     }
 }
 
@@ -335,10 +328,10 @@ class QCalendarYearValidator : public QCalendarDateSectionValidator
 public:
     QCalendarYearValidator();
     virtual Section handleKey(int key) override;
-    virtual QDate applyToDate(const QDate &date) const override;
-    virtual void setDate(const QDate &date) override;
+    virtual QDate applyToDate(const QDate &date, QCalendar cal) const override;
+    virtual void setDate(const QDate &date, QCalendar cal) override;
     virtual QString text() const override;
-    virtual QString text(const QDate &date, int repeat) const override;
+    virtual QString text(const QDate &date, QCalendar cal, int repeat) const override;
 private:
     int pow10(int n);
     int m_pos;
@@ -349,6 +342,8 @@ private:
 QCalendarYearValidator::QCalendarYearValidator()
     : QCalendarDateSectionValidator(), m_pos(0), m_year(2000), m_oldYear(2000)
 {
+    // TODO: What to use (for non-Gregorian calendars) as default year?
+    // Maybe 1360 for Jalali, 1420 for Islamic, etc.
 }
 
 int QCalendarYearValidator::pow10(int n)
@@ -397,21 +392,20 @@ QCalendarDateSectionValidator::Section QCalendarYearValidator::handleKey(int key
     return QCalendarDateSectionValidator::ThisSection;
 }
 
-QDate QCalendarYearValidator::applyToDate(const QDate &date) const
+QDate QCalendarYearValidator::applyToDate(const QDate &date, QCalendar cal) const
 {
-    int year = m_year;
-    if (year < 1)
-        year = 1;
-    QDate newDate(year, date.month(), 1);
-    int day = date.day();
-    if (day > newDate.daysInMonth())
-        day = newDate.daysInMonth();
-    return QDate(year, date.month(), day);
+    auto parts = cal.partsFromDate(date);
+    if (!parts.isValid())
+        return QDate();
+    // This widget does not support negative years (some calendars may support)
+    parts.year = qMax(1, m_year);
+    parts.day = qMin(parts.day, cal.daysInMonth(parts.year, parts.month));
+    return cal.dateFromParts(parts);
 }
 
-void QCalendarYearValidator::setDate(const QDate &date)
+void QCalendarYearValidator::setDate(const QDate &date, QCalendar cal)
 {
-    m_year = m_oldYear = date.year();
+    m_year = m_oldYear = date.year(cal);
     m_pos = 0;
 }
 
@@ -420,11 +414,11 @@ QString QCalendarYearValidator::text() const
     return highlightString(formatNumber(m_year, 4), m_pos);
 }
 
-QString QCalendarYearValidator::text(const QDate &date, int repeat) const
+QString QCalendarYearValidator::text(const QDate &date, QCalendar cal, int repeat) const
 {
     if (repeat < 4)
-        return formatNumber(date.year() % 100, 2);
-    return QString::number(date.year());
+        return formatNumber(date.year(cal) % 100, 2);
+    return QString::number(date.year(cal));
 }
 
 ///////////////////////////////////
@@ -446,18 +440,18 @@ public:
     QCalendarDateValidator();
     ~QCalendarDateValidator();
 
-    void handleKeyEvent(QKeyEvent *keyEvent);
-    QString currentText() const;
+    void handleKeyEvent(QKeyEvent *keyEvent, QCalendar cal);
+    QString currentText(QCalendar cal) const;
     QDate currentDate() const { return m_currentDate; }
     void setFormat(const QString &format);
-    void setInitialDate(const QDate &date);
+    void setInitialDate(const QDate &date, QCalendar cal);
 
     void setLocale(const QLocale &locale);
 
 private:
     void toNextToken();
     void toPreviousToken();
-    void applyToDate();
+    void applyToDate(QCalendar cal);
 
     int countRepeat(const QString &str, int index) const;
     void clear();
@@ -507,17 +501,17 @@ int QCalendarDateValidator::countRepeat(const QString &str, int index) const
     return count;
 }
 
-void QCalendarDateValidator::setInitialDate(const QDate &date)
+void QCalendarDateValidator::setInitialDate(const QDate &date, QCalendar cal)
 {
-    m_yearValidator.setDate(date);
-    m_monthValidator.setDate(date);
-    m_dayValidator.setDate(date);
+    m_yearValidator.setDate(date, cal);
+    m_monthValidator.setDate(date, cal);
+    m_dayValidator.setDate(date, cal);
     m_initialDate = date;
     m_currentDate = date;
     m_lastSectionMove = QCalendarDateSectionValidator::ThisSection;
 }
 
-QString QCalendarDateValidator::currentText() const
+QString QCalendarDateValidator::currentText(QCalendar cal) const
 {
     QString str;
     const int numSeps = m_separators.size();
@@ -529,7 +523,7 @@ QString QCalendarDateValidator::currentText() const
             if (i == m_currentToken)
                 str += token.validator->text();
             else
-                str += token.validator->text(m_currentDate, token.repeat);
+                str += token.validator->text(m_currentDate, cal, token.repeat);
         }
     }
     return str;
@@ -591,11 +585,11 @@ void QCalendarDateValidator::setFormat(const QString &format)
     m_separators += separator;
 }
 
-void QCalendarDateValidator::applyToDate()
+void QCalendarDateValidator::applyToDate(QCalendar cal)
 {
-    m_currentDate = m_yearValidator.applyToDate(m_currentDate);
-    m_currentDate = m_monthValidator.applyToDate(m_currentDate);
-    m_currentDate = m_dayValidator.applyToDate(m_currentDate);
+    m_currentDate = m_yearValidator.applyToDate(m_currentDate, cal);
+    m_currentDate = m_monthValidator.applyToDate(m_currentDate, cal);
+    m_currentDate = m_dayValidator.applyToDate(m_currentDate, cal);
 }
 
 void QCalendarDateValidator::toNextToken()
@@ -614,7 +608,7 @@ void QCalendarDateValidator::toPreviousToken()
     m_currentToken %= m_tokens.size();
 }
 
-void QCalendarDateValidator::handleKeyEvent(QKeyEvent *keyEvent)
+void QCalendarDateValidator::handleKeyEvent(QKeyEvent *keyEvent,QCalendar cal)
 {
     if (m_currentToken < 0)
         return;
@@ -631,7 +625,7 @@ void QCalendarDateValidator::handleKeyEvent(QKeyEvent *keyEvent)
 
     m_lastSectionMove = m_tokens[m_currentToken].validator->handleKey(key);
 
-    applyToDate();
+    applyToDate(cal);
     if (m_lastSectionMove == QCalendarDateSectionValidator::NextSection)
         toNextToken();
     else if (m_lastSectionMove == QCalendarDateSectionValidator::PrevSection)
@@ -645,7 +639,8 @@ class QCalendarTextNavigator: public QObject
     Q_OBJECT
 public:
     QCalendarTextNavigator(QObject *parent = 0)
-        : QObject(parent), m_dateText(0), m_dateFrame(0), m_dateValidator(0), m_widget(0), m_editDelay(1500), m_date(QDate::currentDate()) { }
+        : QObject(parent), m_dateText(0), m_dateFrame(0), m_dateValidator(0),
+          m_widget(0), m_editDelay(1500), m_date(QDate::currentDate()) {}
 
     QWidget *widget() const;
     void setWidget(QWidget *widget);
@@ -676,6 +671,7 @@ private:
     int m_editDelay;
 
     QDate m_date;
+    const QCalendar m_calendar;
 };
 
 QWidget *QCalendarTextNavigator::widget() const
@@ -700,7 +696,7 @@ void QCalendarTextNavigator::updateDateLabel()
 
     m_acceptTimer.start(m_editDelay, this);
 
-    m_dateText->setText(m_dateValidator->currentText());
+    m_dateText->setText(m_dateValidator->currentText(m_calendar));
 
     QSize s = m_dateFrame->sizeHint();
     QRect r = m_widget->geometry(); // later, just the table section
@@ -740,7 +736,7 @@ void QCalendarTextNavigator::createDateLabel()
     m_dateValidator = new QCalendarDateValidator();
     m_dateValidator->setLocale(m_widget->locale());
     m_dateValidator->setFormat(m_widget->locale().dateFormat(QLocale::ShortFormat));
-    m_dateValidator->setInitialDate(m_date);
+    m_dateValidator->setInitialDate(m_date, m_calendar);
 
     m_dateFrame->setAutoFillBackground(true);
     m_dateFrame->setBackgroundRole(QPalette::Window);
@@ -775,7 +771,7 @@ bool QCalendarTextNavigator::eventFilter(QObject *o, QEvent *e)
 #endif
                 } else if (e->type() == QEvent::KeyPress) {
                     createDateLabel();
-                    m_dateValidator->handleKeyEvent(ke);
+                    m_dateValidator->handleKeyEvent(ke, m_calendar);
                     updateDateLabel();
                 }
                 ke->accept();
@@ -897,6 +893,9 @@ public:
     void showMonth(int year, int month);
     void setDate(const QDate &d);
 
+    void setCalendar(QCalendar c);
+    QCalendar calendar() const;
+
     void setMinimumDate(const QDate &date);
     void setMaximumDate(const QDate &date);
 
@@ -926,6 +925,7 @@ public:
 
     int m_firstColumn;
     int m_firstRow;
+    QCalendar m_calendar;
     QDate m_date;
     QDate m_minimumDate;
     QDate m_maximumDate;
@@ -984,8 +984,8 @@ QCalendarModel::QCalendarModel(QObject *parent)
       m_date(QDate::currentDate()),
       m_minimumDate(QDate::fromJulianDay(1)),
       m_maximumDate(9999, 12, 31),
-      m_shownYear(m_date.year()),
-      m_shownMonth(m_date.month()),
+      m_shownYear(m_date.year(m_calendar)),
+      m_shownMonth(m_date.month(m_calendar)),
       m_firstDay(QLocale().firstDayOfWeek()),
       m_horizontalHeaderFormat(QCalendarWidget::ShortDayNames),
       m_weekNumbersShown(true),
@@ -1028,9 +1028,10 @@ will be rendered in 2nd or 3rd row, showing more dates from previous month.
 */
 QDate QCalendarModel::referenceDate() const
 {
+    // TODO: Check this
     int refDay = 1;
     while (refDay <= 31) {
-        QDate refDate(m_shownYear, m_shownMonth, refDay);
+        QDate refDate(m_shownYear, m_shownMonth, refDay, m_calendar);
         if (refDate.isValid())
             return refDate;
         refDay += 1;
@@ -1040,7 +1041,8 @@ QDate QCalendarModel::referenceDate() const
 
 int QCalendarModel::columnForFirstOfMonth(const QDate &date) const
 {
-    return (columnForDayOfWeek(static_cast<Qt::DayOfWeek>(date.dayOfWeek())) - (date.day() % 7) + 8) % 7;
+    return (columnForDayOfWeek(static_cast<Qt::DayOfWeek>(m_calendar.dayOfWeek(date)))
+            - (date.day(m_calendar) % 7) + 8) % 7;
 }
 
 QDate QCalendarModel::dateForCell(int row, int column) const
@@ -1056,7 +1058,8 @@ QDate QCalendarModel::dateForCell(int row, int column) const
     if (columnForFirstOfShownMonth - m_firstColumn < MinimumDayOffset)
         row -= 1;
 
-    const int requestedDay = 7 * (row - m_firstRow) + column - columnForFirstOfShownMonth - refDate.day() + 1;
+    const int requestedDay =
+        7 * (row - m_firstRow) + column - columnForFirstOfShownMonth - refDate.day(m_calendar) + 1;
     return refDate.addDays(requestedDay);
 }
 
@@ -1075,7 +1078,8 @@ void QCalendarModel::cellForDate(const QDate &date, int *row, int *column) const
         return;
 
     const int columnForFirstOfShownMonth = columnForFirstOfMonth(refDate);
-    const int requestedPosition = refDate.daysTo(date) - m_firstColumn + columnForFirstOfShownMonth + refDate.day() - 1;
+    const int requestedPosition = (refDate.daysTo(date) - m_firstColumn +
+                                   columnForFirstOfShownMonth + refDate.day(m_calendar) - 1);
 
     int c = requestedPosition % 7;
     int r = requestedPosition / 7;
@@ -1148,7 +1152,7 @@ QTextCharFormat QCalendarModel::formatForCell(int row, int col) const
         format.merge(m_dateFormats.value(date));
         if(date < m_minimumDate || date > m_maximumDate)
             format.setBackground(pal.brush(cg, QPalette::Window));
-        if (m_shownMonth != date.month())
+        if (m_shownMonth != date.month(m_calendar))
             format.setForeground(pal.brush(QPalette::Disabled, QPalette::Text));
     }
     return format;
@@ -1174,7 +1178,7 @@ QVariant QCalendarModel::data(const QModelIndex &index, int role) const
             return dayName(dayOfWeekForColumn(column));
         QDate date = dateForCell(row, column);
         if (date.isValid())
-            return date.day();
+            return date.day(m_calendar);
         return QString();
     }
 
@@ -1211,6 +1215,20 @@ void QCalendarModel::setDate(const QDate &d)
         m_date = m_maximumDate;
 }
 
+void QCalendarModel::setCalendar(QCalendar c)
+{
+    m_calendar = c;
+    m_shownYear = m_date.year(c);
+    m_shownMonth = m_date.month(c);
+    internalUpdate();
+    m_view->internalUpdate();
+}
+
+QCalendar QCalendarModel::calendar() const
+{
+    return m_calendar;
+}
+
 void QCalendarModel::showMonth(int year, int month)
 {
     if (m_shownYear == year && m_shownMonth == month)
@@ -1341,6 +1359,8 @@ QModelIndex QCalendarView::moveCursor(CursorAction cursorAction, Qt::KeyboardMod
     if (!calendarModel)
         return QTableView::moveCursor(cursorAction, modifiers);
 
+    QCalendar cal = calendarModel->calendar();
+
     if (readOnly)
         return currentIndex();
 
@@ -1359,17 +1379,27 @@ QModelIndex QCalendarView::moveCursor(CursorAction cursorAction, Qt::KeyboardMod
         case QAbstractItemView::MoveRight:
             currentDate = currentDate.addDays(isRightToLeft() ? -1 : 1);
             break;
-        case QAbstractItemView::MoveHome:
-            currentDate = QDate(currentDate.year(), currentDate.month(), 1);
+        case QAbstractItemView::MoveHome: {
+            auto parts = cal.partsFromDate(currentDate);
+            if (parts.isValid()) {
+                parts.day = 1;
+                currentDate = cal.dateFromParts(parts);
+            }
+        }
             break;
-        case QAbstractItemView::MoveEnd:
-            currentDate = QDate(currentDate.year(), currentDate.month(), currentDate.daysInMonth());
+        case QAbstractItemView::MoveEnd: {
+            auto parts = cal.partsFromDate(currentDate);
+            if (parts.isValid()) {
+                parts.day = cal.daysInMonth(parts.year, parts.month);
+                currentDate = cal.dateFromParts(parts);
+            }
+        }
             break;
         case QAbstractItemView::MovePageUp:
-            currentDate = currentDate.addMonths(-1);
+            currentDate = currentDate.addMonths(-1, cal);
             break;
         case QAbstractItemView::MovePageDown:
-            currentDate = currentDate.addMonths(1);
+            currentDate = currentDate.addMonths(1, cal);
             break;
         case QAbstractItemView::MoveNext:
         case QAbstractItemView::MovePrevious:
@@ -1422,8 +1452,9 @@ void QCalendarView::wheelEvent(QWheelEvent *event)
     const int numDegrees = event->angleDelta().y() / 8;
     const int numSteps = numDegrees / 15;
     const QModelIndex index = currentIndex();
-    QDate currentDate = static_cast<QCalendarModel*>(model())->dateForCell(index.row(), index.column());
-    currentDate = currentDate.addMonths(-numSteps);
+    QCalendarModel *calendarModel = static_cast<QCalendarModel*>(model());
+    QDate currentDate = calendarModel->dateForCell(index.row(), index.column());
+    currentDate = currentDate.addMonths(-numSteps, calendarModel->calendar());
     emit showDate(currentDate);
 }
 #endif
@@ -1756,7 +1787,7 @@ void QCalendarWidgetPrivate::createNavigationBar(QWidget *widget)
     monthButton->setPopupMode(QToolButton::InstantPopup);
     monthMenu = new QMenu(monthButton);
     for (int i = 1; i <= 12; i++) {
-        QString monthName(q->locale().standaloneMonthName(i, QLocale::LongFormat));
+        QString monthName(m_model->m_calendar.standaloneMonthName(q->locale(), i, QLocale::LongFormat));
         QAction *act = monthMenu->addAction(monthName);
         act->setData(i);
         monthToAction[i] = act;
@@ -1772,8 +1803,8 @@ void QCalendarWidgetPrivate::createNavigationBar(QWidget *widget)
     monthButton->setFont(font);
     yearButton->setFont(font);
     yearEdit->setFrame(false);
-    yearEdit->setMinimum(m_model->m_minimumDate.year());
-    yearEdit->setMaximum(m_model->m_maximumDate.year());
+    yearEdit->setMinimum(m_model->m_minimumDate.year(m_model->m_calendar));
+    yearEdit->setMaximum(m_model->m_maximumDate.year(m_model->m_calendar));
     yearEdit->hide();
     spaceHolder = new QSpacerItem(0,0);
 
@@ -1803,7 +1834,7 @@ void QCalendarWidgetPrivate::createNavigationBar(QWidget *widget)
     yearEdit->setObjectName(QLatin1String("qt_calendar_yearedit"));
 
     updateMonthMenu();
-    showMonth(m_model->m_date.year(), m_model->m_date.month());
+    showMonth(m_model->m_date.year(m_model->m_calendar), m_model->m_date.month(m_model->m_calendar));
 }
 
 void QCalendarWidgetPrivate::updateButtonIcons()
@@ -1815,22 +1846,24 @@ void QCalendarWidgetPrivate::updateButtonIcons()
 
 void QCalendarWidgetPrivate::updateMonthMenu()
 {
-    int beg = 1, end = 12;
+    int maxMonths = m_model->m_calendar.monthsInYear(m_model->m_shownYear);
+    int beg = 1, end = maxMonths;
     bool prevEnabled = true;
     bool nextEnabled = true;
-    if (m_model->m_shownYear == m_model->m_minimumDate.year()) {
-        beg = m_model->m_minimumDate.month();
-        if (m_model->m_shownMonth == m_model->m_minimumDate.month())
+    QCalendar cal = m_model->calendar();
+    if (m_model->m_shownYear == m_model->m_minimumDate.year(cal)) {
+        beg = m_model->m_minimumDate.month(cal);
+        if (m_model->m_shownMonth == m_model->m_minimumDate.month(cal))
             prevEnabled = false;
     }
-    if (m_model->m_shownYear == m_model->m_maximumDate.year()) {
-        end = m_model->m_maximumDate.month();
-        if (m_model->m_shownMonth == m_model->m_maximumDate.month())
+    if (m_model->m_shownYear == m_model->m_maximumDate.year(cal)) {
+        end = m_model->m_maximumDate.month(cal);
+        if (m_model->m_shownMonth == m_model->m_maximumDate.month(cal))
             nextEnabled = false;
     }
     prevMonth->setEnabled(prevEnabled);
     nextMonth->setEnabled(nextEnabled);
-    for (int i = 1; i <= 12; i++) {
+    for (int i = 1; i <= maxMonths; i++) {
         bool monthEnabled = true;
         if (i < beg || i > end)
             monthEnabled = false;
@@ -1843,7 +1876,7 @@ void QCalendarWidgetPrivate::updateMonthMenuNames()
     Q_Q(QCalendarWidget);
 
     for (int i = 1; i <= 12; i++) {
-        QString monthName(q->locale().standaloneMonthName(i, QLocale::LongFormat));
+        QString monthName(m_model->m_calendar.standaloneMonthName(q->locale(), i, QLocale::LongFormat));
         monthToAction[i]->setText(monthName);
     }
 }
@@ -1851,6 +1884,7 @@ void QCalendarWidgetPrivate::updateMonthMenuNames()
 void QCalendarWidgetPrivate::updateCurrentPage(const QDate &date)
 {
     Q_Q(QCalendarWidget);
+    QCalendar cal = m_model->calendar();
 
     QDate newDate = date;
     QDate minDate = q->minimumDate();
@@ -1859,7 +1893,7 @@ void QCalendarWidgetPrivate::updateCurrentPage(const QDate &date)
         newDate = minDate;
     if (maxDate.isValid()&& maxDate.daysTo(newDate) > 0)
         newDate = maxDate;
-    showMonth(newDate.year(), newDate.month());
+    showMonth(newDate.year(cal), newDate.month(cal));
     int row = -1, col = -1;
     m_model->cellForDate(newDate, &row, &col);
     if (row != -1 && col != -1)
@@ -1873,7 +1907,7 @@ void QCalendarWidgetPrivate::_q_monthChanged(QAction *act)
 {
     monthButton->setText(act->text());
     QDate currentDate = getCurrentDate();
-    QDate newDate = currentDate.addMonths(act->data().toInt()-currentDate.month());
+    QDate newDate = currentDate.addMonths(act->data().toInt() - currentDate.month(m_model->m_calendar), m_model->m_calendar);
     updateCurrentPage(newDate);
 }
 
@@ -1885,27 +1919,28 @@ QDate QCalendarWidgetPrivate::getCurrentDate()
 
 void QCalendarWidgetPrivate::_q_prevMonthClicked()
 {
-    QDate currentDate = getCurrentDate().addMonths(-1);
+    QDate currentDate = getCurrentDate().addMonths(-1, m_model->m_calendar);
     updateCurrentPage(currentDate);
 }
 
 void QCalendarWidgetPrivate::_q_nextMonthClicked()
 {
-    QDate currentDate = getCurrentDate().addMonths(1);
+    QDate currentDate = getCurrentDate().addMonths(1, m_model->m_calendar);
     updateCurrentPage(currentDate);
 }
 
 void QCalendarWidgetPrivate::_q_yearEditingFinished()
 {
     Q_Q(QCalendarWidget);
-    yearButton->setText(yearEdit->text());
+    yearButton->setText(q->locale().toString(yearEdit->value()));
     yearEdit->hide();
     q->setFocusPolicy(oldFocusPolicy);
     qApp->removeEventFilter(q);
     spaceHolder->changeSize(0, 0);
     yearButton->show();
     QDate currentDate = getCurrentDate();
-    currentDate = currentDate.addYears(yearEdit->text().toInt() - currentDate.year());
+    int newYear = q->locale().toInt(yearEdit->text());
+    currentDate = currentDate.addYears(newYear - currentDate.year(m_model->m_calendar), m_model->m_calendar);
     updateCurrentPage(currentDate);
 }
 
@@ -1944,7 +1979,7 @@ void QCalendarWidgetPrivate::updateNavigationBar()
 {
     Q_Q(QCalendarWidget);
 
-    QString monthName = q->locale().standaloneMonthName(m_model->m_shownMonth, QLocale::LongFormat);
+    QString monthName = m_model->m_calendar.standaloneMonthName(q->locale(), m_model->m_shownMonth, QLocale::LongFormat);
 
     monthButton->setText(monthName);
     yearEdit->setValue(m_model->m_shownYear);
@@ -1986,7 +2021,7 @@ void QCalendarWidgetPrivate::_q_slotChangeDate(const QDate &date, bool changeMon
     m_model->setDate(date);
     QDate newDate = m_model->m_date;
     if (changeMonth)
-        showMonth(newDate.year(), newDate.month());
+        showMonth(newDate.year(m_model->m_calendar), newDate.month(m_model->m_calendar));
     if (oldDate != newDate) {
         update();
         Q_Q(QCalendarWidget);
@@ -2242,7 +2277,7 @@ QSize QCalendarWidget::minimumSizeHint() const
         QFontMetrics fm = d->monthButton->fontMetrics();
         int monthW = 0;
         for (int i = 1; i < 12; i++) {
-            QString monthName = locale().standaloneMonthName(i, QLocale::LongFormat);
+            QString monthName = d->m_model->m_calendar.standaloneMonthName(locale(), i, QLocale::LongFormat);
             monthW = qMax(monthW, fm.boundingRect(monthName).width());
         }
         const int buttonDecoMargin = d->monthButton->sizeHint().width() - fm.boundingRect(d->monthButton->text()).width();
@@ -2302,7 +2337,8 @@ void QCalendarWidget::setSelectedDate(const QDate &date)
     d->m_model->setDate(date);
     d->update();
     QDate newDate = d->m_model->m_date;
-    d->showMonth(newDate.year(), newDate.month());
+    QCalendar cal = d->m_model->m_calendar;
+    d->showMonth(newDate.year(cal), newDate.month(cal));
     emit selectionChanged();
 }
 
@@ -2348,14 +2384,15 @@ void QCalendarWidget::setCurrentPage(int year, int month)
 {
     Q_D(QCalendarWidget);
     QDate currentDate = d->getCurrentDate();
-    int day = currentDate.day();
-    int daysInMonths = QDate(year, month, 1).daysInMonth();
+    QCalendar cal = d->m_model->m_calendar;
+    int day = currentDate.day(cal);
+    int daysInMonths = cal.daysInMonth(year, month);
     if (day > daysInMonths)
         day = daysInMonths;
 
     d->showMonth(year, month);
 
-    QDate newDate(year, month, day);
+    QDate newDate(year, month, day, d->m_model->m_calendar);
     int row = -1, col = -1;
     d->m_model->cellForDate(newDate, &row, &col);
     if (row != -1 && col != -1) {
@@ -2373,9 +2410,10 @@ void QCalendarWidget::setCurrentPage(int year, int month)
 
 void QCalendarWidget::showNextMonth()
 {
+    Q_D(const QCalendarWidget);
     int year = yearShown();
     int month = monthShown();
-    if (month == 12) {
+    if (month == d->m_model->m_calendar.maxMonthsInYear()) {
         ++year;
         month = 1;
     } else {
@@ -2393,11 +2431,13 @@ void QCalendarWidget::showNextMonth()
 
 void QCalendarWidget::showPreviousMonth()
 {
+    Q_D(const QCalendarWidget);
+
     int year = yearShown();
     int month = monthShown();
     if (month == 1) {
         --year;
-        month = 12;
+        month = d->m_model->m_calendar.maxMonthsInYear();
     } else {
         --month;
     }
@@ -2443,8 +2483,10 @@ void QCalendarWidget::showPreviousYear()
 */
 void QCalendarWidget::showSelectedDate()
 {
+    Q_D(const QCalendarWidget);
+
     QDate currentDate = selectedDate();
-    setCurrentPage(currentDate.year(), currentDate.month());
+    setCurrentPage(currentDate.year(d->m_model->m_calendar), currentDate.month(d->m_model->m_calendar));
 }
 
 /*!
@@ -2454,8 +2496,10 @@ void QCalendarWidget::showSelectedDate()
 */
 void QCalendarWidget::showToday()
 {
+    Q_D(const QCalendarWidget);
+
     QDate currentDate = QDate::currentDate();
-    setCurrentPage(currentDate.year(), currentDate.month());
+    setCurrentPage(currentDate.year(d->m_model->m_calendar), currentDate.month(d->m_model->m_calendar));
 }
 
 /*!
@@ -2498,12 +2542,12 @@ void QCalendarWidget::setMinimumDate(const QDate &date)
 
     QDate oldDate = d->m_model->m_date;
     d->m_model->setMinimumDate(date);
-    d->yearEdit->setMinimum(d->m_model->m_minimumDate.year());
+    d->yearEdit->setMinimum(d->m_model->m_minimumDate.year(d->m_model->m_calendar));
     d->updateMonthMenu();
     QDate newDate = d->m_model->m_date;
     if (oldDate != newDate) {
         d->update();
-        d->showMonth(newDate.year(), newDate.month());
+        d->showMonth(newDate.year(d->m_model->m_calendar), newDate.month(d->m_model->m_calendar));
         d->m_navigator->setDate(newDate);
         emit selectionChanged();
     }
@@ -2549,12 +2593,12 @@ void QCalendarWidget::setMaximumDate(const QDate &date)
 
     QDate oldDate = d->m_model->m_date;
     d->m_model->setMaximumDate(date);
-    d->yearEdit->setMaximum(d->m_model->m_maximumDate.year());
+    d->yearEdit->setMaximum(d->m_model->m_maximumDate.year(d->m_model->m_calendar));
     d->updateMonthMenu();
     QDate newDate = d->m_model->m_date;
     if (oldDate != newDate) {
         d->update();
-        d->showMonth(newDate.year(), newDate.month());
+        d->showMonth(newDate.year(d->m_model->m_calendar), newDate.month(d->m_model->m_calendar));
         d->m_navigator->setDate(newDate);
         emit selectionChanged();
     }
@@ -2589,13 +2633,13 @@ void QCalendarWidget::setDateRange(const QDate &min, const QDate &max)
 
     QDate oldDate = d->m_model->m_date;
     d->m_model->setRange(min, max);
-    d->yearEdit->setMinimum(d->m_model->m_minimumDate.year());
-    d->yearEdit->setMaximum(d->m_model->m_maximumDate.year());
+    d->yearEdit->setMinimum(d->m_model->m_minimumDate.year(d->m_model->m_calendar));
+    d->yearEdit->setMaximum(d->m_model->m_maximumDate.year(d->m_model->m_calendar));
     d->updateMonthMenu();
     QDate newDate = d->m_model->m_date;
     if (oldDate != newDate) {
         d->update();
-        d->showMonth(newDate.year(), newDate.month());
+        d->showMonth(newDate.year(d->m_model->m_calendar), newDate.month(d->m_model->m_calendar));
         d->m_navigator->setDate(newDate);
         emit selectionChanged();
     }
@@ -2702,6 +2746,22 @@ bool QCalendarWidget::isGridVisible() const
     return d->m_view->showGrid();
 }
 
+QCalendar QCalendarWidget::calendar() const
+{
+    Q_D(const QCalendarWidget);
+    return d->m_model->m_calendar;
+}
+
+void QCalendarWidget::setCalendar(QCalendar c)
+{
+    Q_D(QCalendarWidget);
+    d->m_model->setCalendar(c);
+    d->updateMonthMenuNames();
+    d->yearEdit->setMinimum(d->m_model->m_minimumDate.year(d->m_model->m_calendar));
+    d->yearEdit->setMaximum(d->m_model->m_maximumDate.year(d->m_model->m_calendar));
+    d->updateNavigationBar();
+}
+
 void QCalendarWidget::setGridVisible(bool show)
 {
     Q_D(QCalendarWidget);
@@ -3042,6 +3102,9 @@ bool QCalendarWidget::event(QEvent *event)
             d->updateMonthMenuNames();
             d->updateNavigationBar();
             d->m_view->updateGeometry();
+            // TODO: fix this known bug of calendaring API:
+            // Changing locale before calendar works, but reverse order causes
+            // invalid month names (in C Locale apparently).
             break;
         case QEvent::FontChange:
         case QEvent::ApplicationFontChange: