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diff --git a/src/corelib/time/qislamiccivilcalendar.cpp b/src/corelib/time/qislamiccivilcalendar.cpp
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+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qglobal.h"
+#include "qislamiccivilcalendar_p.h"
+#include "qcalendarmath_p.h"
+#include <QtCore/qmath.h>
+
+QT_BEGIN_NAMESPACE
+
+using namespace QRoundingDown;
+
+/*!
+  \since 5.14
+
+  \class QIslamicCivilCalendar
+  \inmodule QtCore
+  \brief Implements a commonly-used computed version of the Islamic calendar.
+
+  \section1 Civil Islamic Calendar
+
+  QIslamicCivilCalendar implements a tabular version of the Hijri calendar which
+  is known as the Islamic Civil Calendar. It has the same numbering of years and
+  months, but the months are determined by arithmetical rules rather than by
+  observation or astronomical calculations.
+
+  \section2 Calendar Organization
+
+  The civil calendar follows the usual tabular scheme of odd-numbered months and
+  the last month of each leap year being 30 days long, the rest being 29 days
+  long. Its determination of leap years follows a 30-year cycle, in each of
+  which the years 2, 5, 7, 10, 13, 16, 18, 21, 24, 26 and 29 are leap years.
+
+  \sa QJijriCalendar, QCalendar
+*/
+
+QIslamicCivilCalendar::QIslamicCivilCalendar()
+    : QHijriCalendar(QStringLiteral("Islamic Civil"), QCalendar::System::IslamicCivil)
+{
+    registerAlias(QStringLiteral("islamic-civil")); // CLDR name
+    registerAlias(QStringLiteral("islamicc")); // old CLDR name, still (2018) used by Mozilla
+    // Until we have a oncrete implementation that knows all the needed ephemerides:
+    registerAlias(QStringLiteral("Islamic"));
+}
+
+QString QIslamicCivilCalendar::name() const
+{
+    return QStringLiteral("Islamic Civil");
+}
+
+QCalendar::System QIslamicCivilCalendar::calendarSystem() const
+{
+    return QCalendar::System::IslamicCivil;
+}
+
+bool QIslamicCivilCalendar::isLeapYear(int year) const
+{
+    if (year == QCalendar::Unspecified)
+        return false;
+    if (year < 0)
+        ++year;
+    return qMod(year * 11 + 14, 30) < 11;
+}
+
+bool QIslamicCivilCalendar::dateToJulianDay(int year, int month, int day, qint64 *jd) const
+{
+    Q_ASSERT(jd);
+    if (!isDateValid(year, month, day))
+        return false;
+    if (year <= 0)
+        ++year;
+    *jd = qDiv(10631 * year - 10617, 30)
+            + qDiv(325 * month - 320, 11)
+            + day + 1948439;
+    return true;
+}
+
+QCalendar::YearMonthDay QIslamicCivilCalendar::julianDayToDate(qint64 jd) const
+{
+    const qint64 epoch = 1948440;
+    const int32_t k2 = 30 * (jd - epoch) + 15;
+    const int32_t k1 = 11 * qDiv(qMod(k2, 10631), 30) + 5;
+    int y = qDiv(k2, 10631) + 1;
+    const int month = qDiv(k1, 325) + 1;
+    const int day = qDiv(qMod(k1, 325), 11) + 1;
+    return QCalendar::YearMonthDay(y > 0 ? y : y - 1, month, day);
+}
+
+QT_END_NAMESPACE