Add Revised Julian Calendar (#2214)

- Fixed the algorithm error from WP
- Add more tests
- SUG: added notes 

13 files changed, 753 insertions, 130 deletions

diff --git a/guide/plg_calendars.tex b/guide/plg_calendars.tex
index 3d92d19715..923d17d780 100644
--- a/guide/plg_calendars.tex
+++ b/guide/plg_calendars.tex
@@ -66,15 +66,53 @@ dependent on these aspects.
 \subsection{The Calendars}
 \subsubsection{Lunisolar European calendars}
 \begin{description}
-\item[Julian] This implementation utilizes historical year counting,
-  i.e., has no year zero. Years are marked A.D. or B.C., respectively.
+\item[Julian] \name[Julius]{Caesar} introduced this calendar, advised
+  by the Egyptian astronomer \name{Sosigenes}. Every 4th year is a
+  leap year of 366 instead of 365 days, yielding a mean length of the
+  year of 365.25 days.
+
+  In contrast to the default calendar display of Stellarium, this
+  implementation utilizes historical year counting, i.e., has no year
+  zero. Years are marked A.D. or B.C., respectively.  The omission of
+  year zero makes negative leap years break the simple 4-year
+  count. Now they are 1~B.C., 5~B.C., 9~B.C.\ etc. However, note that
+  before 8~A.D.\ leap years are just counted proleptic, but the Romans
+  did not keep the leap years commanded by \name[Julius]{Caesar} until
+  \name{Augustus} put things back in order. This means, displayed
+  dates before 8~A.D.\ may be off by up to 3 days from historical
+  accounts written by contemporaries.
 \item[Gregorian] This implementation acts like Stellarium with respect
-  to year counting and counts negative and positive years, with a year
+  to year counting and counts signed negative and positive years, with a year
   zero between them. It shows dates in a \emph{Proleptic Gregorian}
   calendar for dates before October 15, 1582. Given its improved rules
-  for leap years, it keeps the season's beginnings closer to the
+  for leap years which provide a mean length of the year of 365.2425 days,
+  it keeps the seasons' beginnings closer to the
   commonly known dates, at least for many more centuries in the past
   than the Julian calendar commonly used by historians.
+\item[Revised Julian Calendar] (also named \textbf{Milankovi\'c
+  Calendar}) \newFeature{0.22.0} In 1923, the Serbian scientist
+  \name[Milutin]{Milankovi\'c} (1879--1958) proposed a calendar which
+  should overcome the then 13-day calendar gap between the Eastern
+  European Orthodox churches who still adhered to the Julian calendar
+  and the rest of the world which followed the Gregorian calendar.  It
+  amends the 4-year Julian leap year cycle by omitting century years
+  except for those where division by 900 leaves a remainder of 200 or
+  600.  Therefore the mean length of the year is 365.242\={2} days, 24
+  seconds less than the Gregorian and within 2 seconds of the correct
+  length of the mean tropical year.  For a synchronisation with the
+  Gregorian, October 1-13 1923 were omitted.  Between March 1600 and
+  February 2800 the calendar dates are identical to those in the
+  Gregorian calendar.  The calendar was adopted by several but not all
+  Eastern Orthodox churches, although date of Easter is still computed
+  according to the Julian calendar\footnote{More details can be found on
+    \url{https://en.wikipedia.org/wiki/Revised_Julian_calendar}}.
+
+  In historical context giving dates in the Revised Julian calendar
+  for years before the dates of religious festivals were defined in
+  the calendar makes no sense. Its idea was to have a continuous
+  calendar as it was in use at the concile of Nicaea in
+  A.D.325. Therefore dates before A.D.325 are displayed like in the
+  traditional Julian calendar.
 \item[ISO Week] The International Standards Organization describes
   weeks in the Gregorian calendar from Monday (Day 1) to Sunday (Day
   7). Week 1 of each year contains the first Thursday of the
@@ -244,6 +282,7 @@ settings for the Calendars plugin -- just make it carefully!
 show                         &bool & true\\\midrule
 show\_julian                 &bool & true\\
 show\_gregorian              &bool & true\\
+show\_revised\_julian        &bool & true\\
 show\_iso                    &bool & true\\
 show\_icelandic              &bool & true\\\midrule
 show\_roman                  &bool & true\\
diff --git a/plugins/Calendars/src/CMakeLists.txt b/plugins/Calendars/src/CMakeLists.txt
index f4e024a89b..bb00bb2b6e 100644
--- a/plugins/Calendars/src/CMakeLists.txt
+++ b/plugins/Calendars/src/CMakeLists.txt
@@ -19,6 +19,8 @@ SET(Calendars_SRCS
     ZoroastrianCalendar.cpp
     JulianCalendar.hpp
     JulianCalendar.cpp
+    RevisedJulianCalendar.hpp
+    RevisedJulianCalendar.cpp
     RomanCalendar.hpp
     RomanCalendar.cpp
     OlympicCalendar.hpp
diff --git a/plugins/Calendars/src/Calendar.cpp b/plugins/Calendars/src/Calendar.cpp
index 994a276666..217f697ae4 100644
--- a/plugins/Calendars/src/Calendar.cpp
+++ b/plugins/Calendars/src/Calendar.cpp
@@ -22,6 +22,19 @@
 #include "StelApp.hpp"
 #include "StelCore.hpp"
 
+
+QString Calendar::getFormattedDateString(QVector<int> date, QString sep)
+{
+	QString res;
+	QVector<int>::const_iterator it;
+	for (it=date.constBegin(); it!=date.constEnd(); ++it)
+	{
+		res.append(QString::number(*it));
+		res.append(sep);
+	}
+	return res;
+}
+
 QString Calendar::getFormattedDateString() const
 {
 	return getDateStrings().join(' ');
diff --git a/plugins/Calendars/src/Calendar.hpp b/plugins/Calendars/src/Calendar.hpp
index 66b8c75d58..16e53f38e7 100644
--- a/plugins/Calendars/src/Calendar.hpp
+++ b/plugins/Calendars/src/Calendar.hpp
@@ -81,6 +81,9 @@ public slots:
 	//! get a formatted complete string for a date. The default implementation just concatenates all strings from getDateStrings() with a space in between.
 	virtual QString getFormattedDateString() const;
 
+	//! get a formatted complete string for a date. This implementation just converts and concatenates all ints with sep in between.
+	static QString getFormattedDateString(QVector<int> date, QString sep=" ");
+
 public:
 	constexpr static const double J2000=2451545.0;
 	constexpr static const double jdEpoch=-1721424.5;
diff --git a/plugins/Calendars/src/Calendars.cpp b/plugins/Calendars/src/Calendars.cpp
index 6879d169fb..f04f23f55b 100644
--- a/plugins/Calendars/src/Calendars.cpp
+++ b/plugins/Calendars/src/Calendars.cpp
@@ -33,6 +33,7 @@
 #include "CalendarsDialog.hpp"
 
 #include "JulianCalendar.hpp"
+#include "RevisedJulianCalendar.hpp"
 #include "GregorianCalendar.hpp"
 #include "ISOCalendar.hpp"
 #include "IcelandicCalendar.hpp"
@@ -88,6 +89,7 @@ Calendars::Calendars():
 	toolbarButton(Q_NULLPTR),
 	enabled(true),
 	flagShowJulian(true),
+	flagShowRevisedJulian(true),
 	flagShowGregorian(true),
 	flagShowISO(true),
 	flagShowIcelandic(true),
@@ -192,6 +194,7 @@ void Calendars::init()
 
 	const double jd=StelApp::getInstance().getCore()->getJD();
 	calendars.insert("Julian", new JulianCalendar(jd));
+	calendars.insert("RevisedJulian", new RevisedJulianCalendar(jd));
 	calendars.insert("Gregorian", new GregorianCalendar(jd));
 	calendars.insert("ISO", new ISOCalendar(jd));
 	calendars.insert("Icelandic", new IcelandicCalendar(jd));
@@ -228,6 +231,7 @@ void Calendars::loadSettings()
 	// Now activate calendar displays if needed.
 	enable(                conf->value("Calendars/show", true).toBool());
 	showJulian(            conf->value("Calendars/show_julian", true).toBool());
+	showRevisedJulian(     conf->value("Calendars/show_revised_julian", true).toBool());
 	showGregorian(         conf->value("Calendars/show_gregorian", true).toBool());
 	showISO(               conf->value("Calendars/show_iso", true).toBool());
 	showIcelandic(         conf->value("Calendars/show_icelandic", true).toBool());
@@ -278,28 +282,29 @@ void Calendars::draw(StelCore* core)
 	oss << "<table>";
 	// Select the drawable calendars from GUI or settings.
 	if (calendars.count()==0) return;
-	if (flagShowJulian)             oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Julian",                "calendar"), getCal("Julian")->getFormattedDateString());
-	if (flagShowGregorian)          oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Gregorian",             "calendar"), getCal("Gregorian")->getFormattedDateString());
-	if (flagShowISO)                oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("ISO week",              "calendar"), getCal("ISO")->getFormattedDateString());
-	if (flagShowIcelandic)          oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Icelandic",             "calendar"), getCal("Icelandic")->getFormattedDateString());
-	if (flagShowRoman)              oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Roman",                 "calendar"), getCal("Roman")->getFormattedDateString());
-	if (flagShowOlympic)            oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Olympic",               "calendar"), getCal("Olympic")->getFormattedDateString());
-	if (flagShowEgyptian)           oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Egyptian",              "calendar"), getCal("Egyptian")->getFormattedDateString());
-	if (flagShowArmenian)           oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Armenian",              "calendar"), getCal("Armenian")->getFormattedDateString());
-	if (flagShowZoroastrian)        oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Zoroastrian",           "calendar"), getCal("Zoroastrian")->getFormattedDateString());
-	if (flagShowCoptic)             oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Coptic",                "calendar"), getCal("Coptic")->getFormattedDateString());
-	if (flagShowEthiopic)           oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Ethiopic",              "calendar"), getCal("Ethiopic")->getFormattedDateString());
-	if (flagShowFrenchArithmetic)   oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("French Rev. (Arithm.)", "calendar"), getCal("FrenchArithmetic")->getFormattedDateString());
-	if (flagShowIslamic)            oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Islamic",               "calendar"), getCal("Islamic")->getFormattedDateString());
-	if (flagShowHebrew)             oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Hebrew",                "calendar"), getCal("Hebrew")->getFormattedDateString());
-	if (flagShowPersianArithmetic)  oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Persian (Arithm.)",     "calendar"), getCal("PersianArithmetic")->getFormattedDateString());
-	if (flagShowOldHinduSolar)      oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Old Hindu Solar",       "calendar"), getCal("OldHinduSolar")->getFormattedDateString());
-	if (flagShowOldHinduLunar)      oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Old Hindu Lunisolar",   "calendar"), getCal("OldHinduLunar")->getFormattedDateString());
-	if (flagShowMayaLongCount)      oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Maya Long Count",       "calendar"), getCal("MayaLongCount")->getFormattedDateString());
-	if (flagShowMayaHaab)           oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Maya Haab",             "calendar"), getCal("MayaHaab")->getFormattedDateString());
-	if (flagShowMayaTzolkin)        oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Maya Tzolkin",          "calendar"), getCal("MayaTzolkin")->getFormattedDateString());
-	if (flagShowAztecXihuitl)       oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Aztec Xihuitl",         "calendar"), getCal("AztecXihuitl")->getFormattedDateString());
-	if (flagShowAztecTonalpohualli) oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Aztec Tonalpohualli",   "calendar"), getCal("AztecTonalpohualli")->getFormattedDateString());
+	if (flagShowJulian)             oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Julian",                "calendar"), getCal("Julian")->getFormattedDateString());
+	if (flagShowGregorian)          oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Gregorian",             "calendar"), getCal("Gregorian")->getFormattedDateString());
+	if (flagShowRevisedJulian)      oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Revised Julian",        "calendar"), getCal("RevisedJulian")->getFormattedDateString());
+	if (flagShowISO)                oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("ISO week",              "calendar"), getCal("ISO")->getFormattedDateString());
+	if (flagShowIcelandic)          oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Icelandic",             "calendar"), getCal("Icelandic")->getFormattedDateString());
+	if (flagShowRoman)              oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Roman",                 "calendar"), getCal("Roman")->getFormattedDateString());
+	if (flagShowOlympic)            oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Olympic",               "calendar"), getCal("Olympic")->getFormattedDateString());
+	if (flagShowEgyptian)           oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Egyptian",              "calendar"), getCal("Egyptian")->getFormattedDateString());
+	if (flagShowArmenian)           oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Armenian",              "calendar"), getCal("Armenian")->getFormattedDateString());
+	if (flagShowZoroastrian)        oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Zoroastrian",           "calendar"), getCal("Zoroastrian")->getFormattedDateString());
+	if (flagShowCoptic)             oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Coptic",                "calendar"), getCal("Coptic")->getFormattedDateString());
+	if (flagShowEthiopic)           oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Ethiopic",              "calendar"), getCal("Ethiopic")->getFormattedDateString());
+	if (flagShowFrenchArithmetic)   oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("French Rev. (Arithm.)", "calendar"), getCal("FrenchArithmetic")->getFormattedDateString());
+	if (flagShowIslamic)            oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Islamic",               "calendar"), getCal("Islamic")->getFormattedDateString());
+	if (flagShowHebrew)             oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Hebrew",                "calendar"), getCal("Hebrew")->getFormattedDateString());
+	if (flagShowPersianArithmetic)  oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Persian (Arithm.)",     "calendar"), getCal("PersianArithmetic")->getFormattedDateString());
+	if (flagShowOldHinduSolar)      oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Old Hindu Solar",       "calendar"), getCal("OldHinduSolar")->getFormattedDateString());
+	if (flagShowOldHinduLunar)      oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Old Hindu Lunisolar",   "calendar"), getCal("OldHinduLunar")->getFormattedDateString());
+	if (flagShowMayaLongCount)      oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Maya Long Count",       "calendar"), getCal("MayaLongCount")->getFormattedDateString());
+	if (flagShowMayaHaab)           oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Maya Haab",             "calendar"), getCal("MayaHaab")->getFormattedDateString());
+	if (flagShowMayaTzolkin)        oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Maya Tzolkin",          "calendar"), getCal("MayaTzolkin")->getFormattedDateString());
+	if (flagShowAztecXihuitl)       oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Aztec Xihuitl",         "calendar"), getCal("AztecXihuitl")->getFormattedDateString());
+	if (flagShowAztecTonalpohualli) oss << QString("<tr><td>%1&nbsp;</td><td>%2</td></tr>").arg(qc_("Aztec Tonalpohualli",   "calendar"), getCal("AztecTonalpohualli")->getFormattedDateString());
 	if (flagShowBalinese)      {
 		oss << QString("<tr><td>%1</td><td>%2</td></tr>").arg(qc_("Balinese Pawukon", "calendar"), static_cast<BalinesePawukonCalendar*>(getCal("Balinese"))->getFormattedDateString1to5());
 		oss << QString("<tr><td>  </td><td>%1</td></tr>").arg(static_cast<BalinesePawukonCalendar*>(getCal("Balinese"))->getFormattedDateString6to10());
@@ -362,6 +367,16 @@ void Calendars::showJulian(bool b)
 		emit showJulianChanged(b);
 	}
 }
+bool Calendars::isRevisedJulianDisplayed() const { return flagShowRevisedJulian;}
+void Calendars::showRevisedJulian(bool b)
+{
+	if (b!=flagShowRevisedJulian)
+	{
+		flagShowRevisedJulian=b;
+		conf->setValue("Calendars/show_revised_julian", b);
+		emit showJulianChanged(b);
+	}
+}
 bool Calendars::isGregorianDisplayed() const { return flagShowGregorian;}
 void Calendars::showGregorian(bool b)
 {
diff --git a/plugins/Calendars/src/Calendars.hpp b/plugins/Calendars/src/Calendars.hpp
index b81e1f8f9c..235e66a313 100644
--- a/plugins/Calendars/src/Calendars.hpp
+++ b/plugins/Calendars/src/Calendars.hpp
@@ -37,6 +37,7 @@ class Calendars : public StelModule
 	Q_OBJECT
 	Q_PROPERTY(bool enabled		      READ isEnabled                WRITE enable            NOTIFY enabledChanged)
 	Q_PROPERTY(bool flagShowJulian        READ isJulianDisplayed        WRITE showJulian        NOTIFY showJulianChanged)
+	Q_PROPERTY(bool flagShowRevisedJulian READ isRevisedJulianDisplayed WRITE showRevisedJulian NOTIFY showRevisedJulianChanged)
 	Q_PROPERTY(bool flagShowGregorian     READ isGregorianDisplayed     WRITE showGregorian     NOTIFY showGregorianChanged)
 	Q_PROPERTY(bool flagShowISO           READ isISODisplayed           WRITE showISO           NOTIFY showISOChanged)
 	Q_PROPERTY(bool flagShowIcelandic     READ isIcelandicDisplayed     WRITE showIcelandic     NOTIFY showIcelandicChanged)
@@ -101,6 +102,7 @@ signals:
 
 	void enabledChanged(bool b);
 	void showJulianChanged(bool b);
+	void showRevisedJulianChanged(bool b);
 	void showGregorianChanged(bool b);
 	void showISOChanged(bool b);
 	void showIcelandicChanged(bool b);
@@ -133,6 +135,8 @@ public slots:
 	void enable(bool b);
 	bool isJulianDisplayed() const;		//!< display Julian Calendar?
 	void showJulian(bool b);		//!< activate display of Julian Calendar
+	bool isRevisedJulianDisplayed() const;	//!< display Revised Julian Calendar?
+	void showRevisedJulian(bool b);		//!< activate display of Revised Julian Calendar
 	bool isGregorianDisplayed() const;	//!< display Gregorian Calendar?
 	void showGregorian(bool b);		//!< activate display of Gregorian Calendar
 	bool isISODisplayed() const;		//!< display ISO Calendar?
@@ -198,6 +202,7 @@ private:
 	// StelProperties:
 	bool enabled;
 	bool flagShowJulian;
+	bool flagShowRevisedJulian;
 	bool flagShowGregorian;
 	bool flagShowISO;
 	bool flagShowIcelandic;
diff --git a/plugins/Calendars/src/GregorianCalendar.hpp b/plugins/Calendars/src/GregorianCalendar.hpp
index 97b6182412..0c827ae55e 100644
--- a/plugins/Calendars/src/GregorianCalendar.hpp
+++ b/plugins/Calendars/src/GregorianCalendar.hpp
@@ -56,7 +56,7 @@ public:
 	//! returns true for leap years
 	static bool isLeap(int year);
 
-	constexpr static const int gregorianEpoch=1;  //! RD of January 1, AD1.
+	constexpr static const int gregorianEpoch=1;  //! RD of January 1, AD1 (greg).
 	//! auxiliary functions from CC.UE ch2.5
 	//! Return R.D. of date in the Gregorian calendar.
 	static int fixedFromGregorian(QVector<int> gregorian);
diff --git a/plugins/Calendars/src/JulianCalendar.hpp b/plugins/Calendars/src/JulianCalendar.hpp
index d14f885b27..cb67172b58 100644
--- a/plugins/Calendars/src/JulianCalendar.hpp
+++ b/plugins/Calendars/src/JulianCalendar.hpp
@@ -68,7 +68,7 @@ public:
 	//! find date in the Julian calendar from RD number (may be used in other calendars!)
 	static QVector<int> julianFromFixed(int rd);
 
-	constexpr static const int julianEpoch=-1; //! RD of January 1, AD1.
+	constexpr static const int julianEpoch=-1; //! RD of January 1, AD1 (jul.).
 
 protected:
 	static QMap<int, QString> weekDayNames;
diff --git a/plugins/Calendars/src/RevisedJulianCalendar.cpp b/plugins/Calendars/src/RevisedJulianCalendar.cpp
new file mode 100644
index 0000000000..c00d924cf5
--- /dev/null
+++ b/plugins/Calendars/src/RevisedJulianCalendar.cpp
@@ -0,0 +1,124 @@
+/*
+ * Copyright (C) 2022 Georg Zotti
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335, USA.
+ */
+
+#include "StelTranslator.hpp"
+#include "RevisedJulianCalendar.hpp"
+#include "StelUtils.hpp"
+#include "StelApp.hpp"
+#include "StelCore.hpp"
+
+RevisedJulianCalendar::RevisedJulianCalendar(double jd): JulianCalendar(jd)
+{
+}
+
+// Set a calendar date from the Julian day number
+void RevisedJulianCalendar::setJD(double JD)
+{
+	this->JD=JD;
+
+	int rd=fixedFromJD(JD, true);
+	parts=revisedJulianFromFixed(rd);
+
+	emit partsChanged(parts);
+}
+
+// set date from a vector of calendar date elements sorted from the largest to the smallest.
+// Year-Month[1...12]-Day[1...31]
+// Time is not changed!
+void RevisedJulianCalendar::setDate(QVector<int> parts)
+{
+	//qDebug() << "RevisedJulianCalendar::setDate:" << parts;
+	this->parts=parts;
+	// For the Julian calendar, we really have no year 0 in this plugin.
+	Q_ASSERT(parts.at(0) != 0);
+
+	double rd=fixedFromRevisedJulian(parts);
+	// restore time from JD!
+	double frac=StelUtils::fmodpos(JD+0.5+StelApp::getInstance().getCore()->getUTCOffset(JD)/24., 1.);
+	JD=jdFromFixed(rd+frac, true);
+
+	emit jdChanged(JD);
+}
+
+// returns true for leap years. The algorithm only works correctly for positive years!
+// But we make the switchover in 325.
+bool RevisedJulianCalendar::isLeap(int year)
+{
+	if (year<325)
+		return JulianCalendar::isLeap(year);
+
+	bool leap= (StelUtils::imod(year, 4) == 0);
+	if (leap && (StelUtils::imod(year, 100) == 0))
+	{
+		int century=StelUtils::imod(year, 900);
+		leap=(century==200) || (century==600);
+	}
+	return leap;
+}
+
+int RevisedJulianCalendar::fixedFromRevisedJulian(QVector<int> revisedJulian)
+{
+	const int year=revisedJulian.at(0);
+	const int month=revisedJulian.at(1);
+	const int day=revisedJulian.at(2);
+	// Year BC make no sense here! Don't bother dealing with the leap years...
+	// But note that the calendars were parallel in 325 (Nicaea)
+	if (year<325)
+		return JulianCalendar::fixedFromJulian(revisedJulian);
+
+	const int priorYear=year-1;
+	int fixedDay=revisedJulianEpoch+365*priorYear+StelUtils::intFloorDiv(priorYear,4)+StelUtils::intFloorDiv(367*month-362, 12)+day-1;
+	// If month is after February then subtract 1 day for a leap year or subtract 2 days for a common year:
+	if (month>2)
+		fixedDay -= isLeap(year) ? 1 : 2;
+	// Finally subtract a day for each prior century year (most of which are non-leap) and then add back in the number of prior century leap years:
+	int priorCenturies=StelUtils::intFloorDiv(priorYear, 100);
+	fixedDay += -priorCenturies + StelUtils::intFloorDiv(2*priorCenturies+6, 9);
+	return fixedDay;
+}
+
+QVector<int> RevisedJulianCalendar::revisedJulianFromFixed(int rd)
+{
+	static const int rd325=fixedFromJulian({325, 6, 30});
+	if (rd<rd325)
+		return JulianCalendar::julianFromFixed(rd);
+	const int days = rd-revisedJulianEpoch+1;
+	const int priorCenturies = StelUtils::intFloorDiv(days, 36524);                              // n100 in Gregorian algorithm
+	int remainingDays = days-36524*priorCenturies-StelUtils::intFloorDiv(2*priorCenturies+6, 9); //
+	const int priorSubcycles = StelUtils::intFloorDiv(remainingDays, 1461);                      // n4 in Gregorian algorithm
+	remainingDays = StelUtils::imod(remainingDays,1461);                                         // d3
+	const int priorSubcycleYears = StelUtils::intFloorDiv(remainingDays, 365);                   // n1
+	int year = 100 * priorCenturies + 4 * priorSubcycles + priorSubcycleYears;
+	// Add a correction which was omitted in Wikipedia!
+	if ( !((priorSubcycleYears==4) || (priorCenturies==2)))
+		year+=1;
+
+	remainingDays = StelUtils::imod(remainingDays, 365);
+	if (remainingDays == 0)
+	{
+	    //This is either the 365th day of a common year, or the 365th or 366th day of a leap year. Either way, we have to decrement the year because we went one year too far:
+	    year--;
+	    remainingDays = isLeap(year) && (priorSubcycles==0) ? 366 : 365;
+	}
+	int priorDays = remainingDays - 1;
+	int correction = isLeap(year) ? 1 : 0;
+	correction = (priorDays < (31+28+correction)) ? 0 : 2 - correction;
+	int month = StelUtils::intFloorDiv((12 * (priorDays + correction) + 373) , 367);
+	const int day=rd-fixedFromRevisedJulian({year, month, 1})+1;
+	return {year, month, day};
+}
diff --git a/plugins/Calendars/src/RevisedJulianCalendar.hpp b/plugins/Calendars/src/RevisedJulianCalendar.hpp
new file mode 100644
index 0000000000..9b43ba1306
--- /dev/null
+++ b/plugins/Calendars/src/RevisedJulianCalendar.hpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2022 Georg Zotti
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA  02110-1335, USA.
+ */
+
+#ifndef REVISEDJULIANCALENDAR_HPP
+#define REVISEDJULIANCALENDAR_HPP
+
+#include "JulianCalendar.hpp"
+
+//! The Orthodox Church worked out a Revised Julian Calendar in 1923 to overcome the 13-day gap between their traditional Julian and the rest of the world which is using the Gregorian.
+//! In this calendar, only centuries where division by 900 yields 200 or 600 are leap years.
+//! Dates from March 1st, 1600 to February 28th, 2800, go in sync with the Gregorian calendar.
+//! The algorithm implemented here was taken from https://en.wikipedia.org/wiki/Revised_Julian_calendar in January 2022 (with a necessary fix discovered during implementation)
+//! @note Behaviour of this calendar for dates BC is not documented.
+//! In the first century, dates are 2 days away from the Julian.
+//! Around the Nicaean concile (AD325) this calendar provides the same dates as the Julian, therefore we make the switchover in AD325, and forward all earlier dates to the Julian calendar.
+
+class RevisedJulianCalendar : public JulianCalendar
+{
+	Q_OBJECT
+
+public:
+	RevisedJulianCalendar(double jd);
+	virtual ~RevisedJulianCalendar() Q_DECL_OVERRIDE {}
+
+public slots:
+	//! Set a calendar date from the Julian day number
+	virtual void setJD(double JD) Q_DECL_OVERRIDE;
+
+	//! set date from a vector of calendar date elements sorted from the largest to the smallest.
+	//! Year-Month[1...12]-Day[1...31]
+	virtual void setDate(QVector<int> parts) Q_DECL_OVERRIDE;
+
+public:
+	//! returns true for leap years. We handle years prior to 325 like in the regular Julian calendar.
+	static bool isLeap(int year);
+
+	//! find RD number for date in the Revised Julian calendar. Dates before AD325 are handled as dates in the regular Julian calendar.
+	static int fixedFromRevisedJulian(QVector<int> revisedJulian);
+	//! find date in the Revised Julian calendar from RD number. If date is earlier than AD325,
+	//! the returned date is in the standard Julian Calendar.
+	static QVector<int> revisedJulianFromFixed(int rd);
+
+	constexpr static const int revisedJulianEpoch=1; //! RD of January 1, AD1.
+};
+
+#endif
diff --git a/plugins/Calendars/src/gui/CalendarsDialog.cpp b/plugins/Calendars/src/gui/CalendarsDialog.cpp
index 1bbaa6e4db..eb6be4bbeb 100644
--- a/plugins/Calendars/src/gui/CalendarsDialog.cpp
+++ b/plugins/Calendars/src/gui/CalendarsDialog.cpp
@@ -77,11 +77,17 @@ void CalendarsDialog::createDialogContent()
 	connect(ui->restoreDefaultsButton, SIGNAL(clicked()), this, SLOT(resetCalendarsSettings()));
 	setAboutHtml();
 
-	// DISABLE Chinese for now, TBD!
+#ifdef STELLARIUM_RELEASE_BUILD
+	ui->labelRDvalue->hide();
+	ui->labelRD->hide();
+	// DISABLE Chinese etc for now, TBD!
 	ui->chineseCheckBox->hide();
 	ui->tabs->removeTab(2);
 	ui->newHinduLunarCheckBox->hide();
 	ui->newHinduSolarCheckBox->hide();
+#else
+	connect(cal->getCal("Julian"), &JulianCalendar::jdChanged, this, [=](double jd){ui->labelRDvalue->setText(QString::number(Calendar::fixedFromJD(jd)));});
+#endif
 
 	// MAKE SURE to connect each calendar's partsChanged to a respective populate... method here.
 	connect(cal->getCal("Julian"),             SIGNAL(partsChanged(QVector<int>)), this, SLOT(populateJulianParts(QVector<int>)));
@@ -95,6 +101,7 @@ void CalendarsDialog::createDialogContent()
 	//connect(cal->getCal("Chinese"), SIGNAL(partsChanged(QVector<int>)), this, SLOT(populateChineseParts(QVector<int>)));
 
 	connectBoolProperty(ui->julianCheckBox,             "Calendars.flagShowJulian");
+	connectBoolProperty(ui->revisedJulianCheckBox,      "Calendars.flagShowRevisedJulian");
 	connectBoolProperty(ui->gregorianCheckBox,          "Calendars.flagShowGregorian");
 	connectBoolProperty(ui->isoCheckBox,                "Calendars.flagShowISO");
 	connectBoolProperty(ui->romanCheckBox,              "Calendars.flagShowRoman");
@@ -167,6 +174,7 @@ void CalendarsDialog::setAboutHtml(void)
 	html += "<p>" + q_("The Calendars plugin provides an interface to various calendars used around the world.") + "</p>";
 	html += "<ul><li>" + q_("Julian Calendar") + "</li>";
 	html += "<li>" + q_("Gregorian Calendar") + "</li>";
+	html += "<li>" + q_("Revised Julian Calendar (Milankovi&cacute;)") + "</li>";
 	html += "<li>" + q_("ISO Weeks") + "</li>";
 	html += "<li>" + q_("Icelandic calendar") + "</li>";
 	html += "<li>" + q_("Roman (Julian) calendar") + "</li>";
diff --git a/plugins/Calendars/src/gui/calendarsDialog.ui b/plugins/Calendars/src/gui/calendarsDialog.ui
index 0ee3897323..d118e5cc7a 100644
--- a/plugins/Calendars/src/gui/calendarsDialog.ui
+++ b/plugins/Calendars/src/gui/calendarsDialog.ui
@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>558</width>
-    <height>405</height>
+    <height>419</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -154,13 +154,6 @@
            </property>
           </widget>
          </item>
-         <item row="1" column="0">
-          <widget class="QCheckBox" name="romanCheckBox">
-           <property name="text">
-            <string comment="calendar">Roman</string>
-           </property>
-          </widget>
-         </item>
          <item row="10" column="0">
           <widget class="QCheckBox" name="balineseCheckBox">
            <property name="text">
@@ -175,13 +168,6 @@
            </property>
           </widget>
          </item>
-         <item row="0" column="2">
-          <widget class="QCheckBox" name="isoCheckBox">
-           <property name="text">
-            <string comment="calendar">ISO Week</string>
-           </property>
-          </widget>
-         </item>
          <item row="9" column="1">
           <widget class="QCheckBox" name="newHinduLunarCheckBox">
            <property name="text">
@@ -217,13 +203,6 @@
            </property>
           </widget>
          </item>
-         <item row="2" column="2">
-          <widget class="QCheckBox" name="zoroastrianCheckBox">
-           <property name="text">
-            <string comment="calendar">Zoroastrian</string>
-           </property>
-          </widget>
-         </item>
          <item row="9" column="0">
           <widget class="QCheckBox" name="newHinduSolarCheckBox">
            <property name="text">
@@ -287,13 +266,6 @@
            </property>
           </widget>
          </item>
-         <item row="1" column="2">
-          <widget class="QCheckBox" name="icelandicCheckBox">
-           <property name="text">
-            <string comment="calendar">Icelandic</string>
-           </property>
-          </widget>
-         </item>
          <item row="6" column="0">
           <widget class="QCheckBox" name="mayaLCCheckBox">
            <property name="text">
@@ -329,6 +301,41 @@
            </property>
           </widget>
          </item>
+         <item row="3" column="2">
+          <widget class="QCheckBox" name="zoroastrianCheckBox">
+           <property name="text">
+            <string comment="calendar">Zoroastrian</string>
+           </property>
+          </widget>
+         </item>
+         <item row="2" column="2">
+          <widget class="QCheckBox" name="icelandicCheckBox">
+           <property name="text">
+            <string comment="calendar">Icelandic</string>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="2">
+          <widget class="QCheckBox" name="isoCheckBox">
+           <property name="text">
+            <string comment="calendar">ISO Week</string>
+           </property>
+          </widget>
+         </item>
+         <item row="0" column="2">
+          <widget class="QCheckBox" name="romanCheckBox">
+           <property name="text">
+            <string comment="calendar">Roman</string>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="0">
+          <widget class="QCheckBox" name="revisedJulianCheckBox">
+           <property name="text">
+            <string>Revised Julian</string>
+           </property>
+          </widget>
+         </item>
         </layout>
        </item>
        <item>
@@ -370,21 +377,18 @@
       <layout class="QVBoxLayout" name="lunisolarVerticalLayout">
        <item>
         <layout class="QGridLayout" name="lunisolarGridLayout">
-         <item row="1" column="4">
-          <widget class="QLineEdit" name="julianWeekdayLineEdit">
-           <property name="enabled">
-            <bool>false</bool>
-           </property>
-           <property name="acceptDrops">
-            <bool>false</bool>
-           </property>
-           <property name="alignment">
-            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+         <item row="0" column="1">
+          <widget class="QLabel" name="labelYear">
+           <property name="text">
+            <string>Year</string>
            </property>
           </widget>
          </item>
-         <item row="2" column="1">
-          <widget class="QSpinBox" name="gregorianYearSpinBox">
+         <item row="1" column="1">
+          <widget class="QSpinBox" name="julianYearSpinBox">
+           <property name="toolTip">
+            <string>Negative years here mark years B.C.</string>
+           </property>
            <property name="alignment">
             <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
            </property>
@@ -406,8 +410,8 @@
            </property>
           </widget>
          </item>
-         <item row="1" column="2">
-          <widget class="QSpinBox" name="julianMonthSpinBox">
+         <item row="3" column="2">
+          <widget class="QSpinBox" name="isoWeekSpinBox">
            <property name="wrapping">
             <bool>true</bool>
            </property>
@@ -418,20 +422,7 @@
             <number>0</number>
            </property>
            <property name="maximum">
-            <number>13</number>
-           </property>
-          </widget>
-         </item>
-         <item row="2" column="4">
-          <widget class="QLineEdit" name="gregorianWeekdayLineEdit">
-           <property name="enabled">
-            <bool>false</bool>
-           </property>
-           <property name="acceptDrops">
-            <bool>false</bool>
-           </property>
-           <property name="alignment">
-            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+            <number>54</number>
            </property>
           </widget>
          </item>
@@ -449,8 +440,8 @@
            </property>
           </widget>
          </item>
-         <item row="2" column="3">
-          <widget class="QSpinBox" name="gregorianDaySpinBox">
+         <item row="2" column="2">
+          <widget class="QSpinBox" name="gregorianMonthSpinBox">
            <property name="wrapping">
             <bool>true</bool>
            </property>
@@ -461,23 +452,36 @@
             <number>0</number>
            </property>
            <property name="maximum">
-            <number>32</number>
+            <number>13</number>
            </property>
           </widget>
          </item>
-         <item row="1" column="3">
-          <widget class="QSpinBox" name="julianDaySpinBox">
-           <property name="wrapping">
-            <bool>true</bool>
-           </property>
+         <item row="2" column="1">
+          <widget class="QSpinBox" name="gregorianYearSpinBox">
            <property name="alignment">
             <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
            </property>
            <property name="minimum">
-            <number>0</number>
+            <number>-100000</number>
            </property>
            <property name="maximum">
-            <number>32</number>
+            <number>100000</number>
+           </property>
+           <property name="value">
+            <number>2000</number>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="4">
+          <widget class="QLineEdit" name="julianWeekdayLineEdit">
+           <property name="enabled">
+            <bool>false</bool>
+           </property>
+           <property name="acceptDrops">
+            <bool>false</bool>
+           </property>
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
            </property>
           </widget>
          </item>
@@ -488,8 +492,8 @@
            </property>
           </widget>
          </item>
-         <item row="3" column="2">
-          <widget class="QSpinBox" name="isoWeekSpinBox">
+         <item row="2" column="3">
+          <widget class="QSpinBox" name="gregorianDaySpinBox">
            <property name="wrapping">
             <bool>true</bool>
            </property>
@@ -500,12 +504,28 @@
             <number>0</number>
            </property>
            <property name="maximum">
-            <number>54</number>
+            <number>32</number>
            </property>
           </widget>
          </item>
-         <item row="2" column="2">
-          <widget class="QSpinBox" name="gregorianMonthSpinBox">
+         <item row="3" column="3">
+          <widget class="QSpinBox" name="isoDaySpinBox">
+           <property name="alignment">
+            <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
+           </property>
+           <property name="minimum">
+            <number>0</number>
+           </property>
+           <property name="maximum">
+            <number>8</number>
+           </property>
+           <property name="value">
+            <number>1</number>
+           </property>
+          </widget>
+         </item>
+         <item row="1" column="2">
+          <widget class="QSpinBox" name="julianMonthSpinBox">
            <property name="wrapping">
             <bool>true</bool>
            </property>
@@ -534,34 +554,24 @@
            </property>
           </widget>
          </item>
-         <item row="1" column="1">
-          <widget class="QSpinBox" name="julianYearSpinBox">
-           <property name="toolTip">
-            <string>Negative years here mark years B.C.</string>
+         <item row="2" column="4">
+          <widget class="QLineEdit" name="gregorianWeekdayLineEdit">
+           <property name="enabled">
+            <bool>false</bool>
+           </property>
+           <property name="acceptDrops">
+            <bool>false</bool>
            </property>
            <property name="alignment">
             <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
            </property>
-           <property name="minimum">
-            <number>-100000</number>
-           </property>
-           <property name="maximum">
-            <number>100000</number>
-           </property>
-           <property name="value">
-            <number>2000</number>
-           </property>
           </widget>
          </item>
-         <item row="0" column="1">
-          <widget class="QLabel" name="labelYear">
-           <property name="text">
-            <string>Year</string>
+         <item row="1" column="3">
+          <widget class="QSpinBox" name="julianDaySpinBox">
+           <property name="wrapping">
+            <bool>true</bool>
            </property>
-          </widget>
-         </item>
-         <item row="3" column="3">
-          <widget class="QSpinBox" name="isoDaySpinBox">
            <property name="alignment">
             <set>Qt::AlignRight|Qt::AlignTrailing|Qt::AlignVCenter</set>
            </property>
@@ -569,10 +579,7 @@
             <number>0</number>
            </property>
            <property name="maximum">
-            <number>8</number>
-           </property>
-           <property name="value">
-            <number>1</number>
+            <number>32</number>
            </property>
           </widget>
          </item>
@@ -589,6 +596,20 @@
            </property>
           </widget>
          </item>
+         <item row="4" column="0">
+          <widget class="QLabel" name="labelRD">
+           <property name="text">
+            <string>Rata Die</string>
+           </property>
+          </widget>
+         </item>
+         <item row="4" column="4">
+          <widget class="QLabel" name="labelRDvalue">
+           <property name="text">
+            <string>RD number</string>
+           </property>
+          </widget>
+         </item>
         </layout>
        </item>
        <item>
diff --git a/plugins/Calendars/src/test/testCalendars.cpp b/plugins/Calendars/src/test/testCalendars.cpp
index ce69455af2..a77142a287 100644
--- a/plugins/Calendars/src/test/testCalendars.cpp
+++ b/plugins/Calendars/src/test/testCalendars.cpp
@@ -28,6 +28,10 @@
 #include "StelUtils.hpp"
 #include "../Calendar.hpp"
 #include "../JulianCalendar.hpp"
+#include "../RevisedJulianCalendar.hpp"
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+#include <QCalendar>
+#endif
 #include "../GregorianCalendar.hpp"
 #include "../ISOCalendar.hpp"
 #include "../IcelandicCalendar.hpp"
@@ -81,14 +85,15 @@ void TestCalendars::testBasics()
 	QVERIFY2(Calendar::modInterval(5, 1, 2)==1, qPrintable(QString("modInterval(5, 1, 2)=%1").arg(QString::number(Calendar::modInterval(5, 1, 2)))));
 	QVERIFY2(Calendar::modInterval(6, 1, 2)==1, qPrintable(QString("modInterval(6, 1, 2)=%1").arg(QString::number(Calendar::modInterval(6, 1, 2)))));
 	// Critically important: modinterval(., 1, n)=amod(., n-1). n is NOT the maximum possible return value!
-	QVERIFY2(Calendar::modInterval(42, 1, 7)==StelUtils::amod(42, 6), qPrintable(QString("modInterval(42, 1, 6)=%1 vs amod(42, 6)=%2").arg(QString::number(Calendar::modInterval(5, 1, 2))).arg(QString::number(StelUtils::amod(42, 6)))));
-	QVERIFY2(Calendar::modInterval(43, 1, 7)==StelUtils::amod(43, 6), qPrintable(QString("modInterval(43, 1, 6)=%1 vs amod(43, 6)=%2").arg(QString::number(Calendar::modInterval(6, 1, 2))).arg(QString::number(StelUtils::amod(43, 6)))));
+	QVERIFY2(Calendar::modInterval(42, 1, 7)==StelUtils::amod(42, 6), qPrintable(QString("modInterval(42, 1, 6)=%1 vs amod(42, 6)=%2").arg(QString::number(Calendar::modInterval(5, 1, 2)), QString::number(StelUtils::amod(42, 6)))));
+	QVERIFY2(Calendar::modInterval(43, 1, 7)==StelUtils::amod(43, 6), qPrintable(QString("modInterval(43, 1, 6)=%1 vs amod(43, 6)=%2").arg(QString::number(Calendar::modInterval(6, 1, 2)), QString::number(StelUtils::amod(43, 6)))));
 	QVERIFY(StelUtils::intFloorDiv(8, 2)==4);
 	QVERIFY(StelUtils::intFloorDiv(8, 3)==2);
 	QVERIFY(StelUtils::intFloorDiv(-8, 3)==-3);
 	QVERIFY(StelUtils::intFloorDiv(-8, -2)==4);
 	QVERIFY(StelUtils::intFloorDiv(-8, 2)==-4);
 	QVERIFY(StelUtils::intFloorDiv(8, -2)==-4);
+	QVERIFY(StelUtils::imod(-1, 100)==99);
 }
 
 void TestCalendars::testEuropean()
@@ -99,6 +104,333 @@ void TestCalendars::testEuropean()
 	QVERIFY(JulianCalendar::fixedFromJulian({1, 1, 1})==JulianCalendar::julianEpoch);
 	QVERIFY(JulianCalendar::fixedFromJulian({1, 1, 1})==GregorianCalendar::fixedFromGregorian({0, JulianCalendar::december, 30}));
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
+	// RevisedJulianCalendar should behave identical to Qt's MilankovicCalendar.
+	QCalendar mil(QCalendar::System::Milankovic);
+	for (int year=400; year<10001; year+=100)
+		QVERIFY(RevisedJulianCalendar::isLeap(year)==mil.isLeapYear(year));
+#endif
+	QVERIFY(RevisedJulianCalendar::isLeap( 400)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap( 500)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap( 600)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap( 700)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap( 800)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap( 900)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1000)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1100)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(1200)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1300)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1400)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1500)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(1600)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1700)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1800)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(1900)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2000)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(2100)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2200)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2300)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2400)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(2500)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2600)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2700)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2800)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(2900)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(3000)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3100)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3200)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3300)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(3400)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3500)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3600)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3700)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(3800)==true);
+	QVERIFY(RevisedJulianCalendar::isLeap(3900)==false);
+	QVERIFY(RevisedJulianCalendar::isLeap(4000)==false);
+	QVERIFY(RevisedJulianCalendar::revisedJulianEpoch==Calendar::fixedFromJD(1721425.5, false));
+	QVERIFY2(qFuzzyCompare(RevisedJulianCalendar::fixedFromRevisedJulian({2000, 1, 1}), 730120.5 - 0.5), // Subtract half-day.
+		 qPrintable(QString("fixed from Revised Julian 1.1.2000: %1 (expected %2)").arg(RevisedJulianCalendar::fixedFromRevisedJulian({2000, 1, 1})).arg(730120.5-0.5, 8, 'f')));
+
+	// Test simple date reversion for all dates 1..28.month.year in sensible range.
+	for (int y=325; y<10799; y++)
+		for (int m=1; m<=12; ++m)
+			for (int d=1; d<29; d++)
+			{
+				QVector<int> date={y, m, d};
+				QVERIFY2(RevisedJulianCalendar::revisedJulianFromFixed(RevisedJulianCalendar::fixedFromRevisedJulian(date)) == date,
+					 qPrintable(QString("Problem with date %1").arg(Calendar::getFormattedDateString(date, ":"))));
+			}
+
+	// Make sure to get the transition right.
+	for (int y=325; y<400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==JulianCalendar::fixedFromJulian({y, m, 1}));
+	// Rest of table from https://en.wikipedia.org/wiki/Revised_Julian_calendar. Note that the arithmetic result is reversed from the list.
+	for (int y=325; y<400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})+1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({400, m, 1})==GregorianCalendar::fixedFromGregorian({400, m, 1})+1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({400, m, 1})==GregorianCalendar::fixedFromGregorian({400, m, 1}));
+	for (int y=401; y<600; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({600, m, 1})==GregorianCalendar::fixedFromGregorian({600, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({600, m, 1})==GregorianCalendar::fixedFromGregorian({600, m, 1})+1);
+	for (int y=601; y<800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})+1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({800, m, 1})==GregorianCalendar::fixedFromGregorian({800, m, 1})+1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({800, m, 1})==GregorianCalendar::fixedFromGregorian({800, m, 1}));
+	for (int y=801; y<1100; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1100, m, 1})==GregorianCalendar::fixedFromGregorian({1100, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1100, m, 1})==GregorianCalendar::fixedFromGregorian({1100, m, 1})+1);
+	for (int y=1101; y<1200; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})+1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1200, m, 1})==GregorianCalendar::fixedFromGregorian({1200, m, 1})+1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1200, m, 1})==GregorianCalendar::fixedFromGregorian({1200, m, 1}));
+	for (int y=1201; y<1500; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1500, m, 1})==GregorianCalendar::fixedFromGregorian({1500, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1500, m, 1})==GregorianCalendar::fixedFromGregorian({1500, m, 1})+1);
+	for (int y=1501; y<1600; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})+1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1600, m, 1})==GregorianCalendar::fixedFromGregorian({1600, m, 1})+1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({1600, m, 1})==GregorianCalendar::fixedFromGregorian({1600, m, 1}));
+	for (int y=1601; y<2800; y++)
+		for (int m=1; m<=12; ++m)
+		{
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+			for (int d=1; d<29; d++)
+			{
+				QVector<int> date={y, m, d};
+				QVERIFY(RevisedJulianCalendar::revisedJulianFromFixed(GregorianCalendar::fixedFromGregorian(date)) == date);
+			}
+		}
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({2800, m, 1})==GregorianCalendar::fixedFromGregorian({2800, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({2800, m, 1})==GregorianCalendar::fixedFromGregorian({2800, m, 1})-1);
+	for (int y=2801; y<2900; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({2900, m, 1})==GregorianCalendar::fixedFromGregorian({2900, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({2900, m, 1})==GregorianCalendar::fixedFromGregorian({2900, m, 1}));
+	for (int y=2901; y<3200; y++)
+		for (int m=1; m<=12; ++m)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3200, m, 1})==GregorianCalendar::fixedFromGregorian({3200, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3300, m, 1})==GregorianCalendar::fixedFromGregorian({3300, m, 1}));
+	for (int y=3301; y<3600; y++)
+		for (int m=1; m<=12; ++m)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3300, 3, 1})==GregorianCalendar::fixedFromGregorian({3300, 3, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3600, m, 1})==GregorianCalendar::fixedFromGregorian({3600, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3600, m, 1})==GregorianCalendar::fixedFromGregorian({3600, m, 1})-1);
+	for (int y=3601; y<3800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3800, m, 1})==GregorianCalendar::fixedFromGregorian({3800, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({3800, m, 1})==GregorianCalendar::fixedFromGregorian({3800, m, 1}));
+	for (int y=3801; y<4000; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4000, m, 1})==GregorianCalendar::fixedFromGregorian({4000, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4000, m, 1})==GregorianCalendar::fixedFromGregorian({4000, m, 1})-1);
+	for (int y=4001; y<4200; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4200, m, 1})==GregorianCalendar::fixedFromGregorian({4200, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4200, m, 1})==GregorianCalendar::fixedFromGregorian({4200, m, 1}));
+	for (int y=4201; y<4400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4400, m, 1})==GregorianCalendar::fixedFromGregorian({4400, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4400, m, 1})==GregorianCalendar::fixedFromGregorian({4400, m, 1})-1);
+	for (int y=4401; y<4700; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4700, m, 1})==GregorianCalendar::fixedFromGregorian({4700, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4700, m, 1})==GregorianCalendar::fixedFromGregorian({4700, m, 1}));
+	for (int y=4701; y<4800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4800, m, 1})==GregorianCalendar::fixedFromGregorian({4800, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({4800, m, 1})==GregorianCalendar::fixedFromGregorian({4800, m, 1})-1);
+	for (int y=4801; y<5100; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({5100, m, 1})==GregorianCalendar::fixedFromGregorian({5100, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({5100, m, 1})==GregorianCalendar::fixedFromGregorian({5100, m, 1}));
+	for (int y=5101; y<5200; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1}));
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({5200, m, 1})==GregorianCalendar::fixedFromGregorian({5200, m, 1}));
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({5200, m, 1})==GregorianCalendar::fixedFromGregorian({5200, m, 1})-1);
+	for (int y=5201; y<6400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6400, m, 1})==GregorianCalendar::fixedFromGregorian({6400, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6400, m, 1})==GregorianCalendar::fixedFromGregorian({6400, m, 1})-2);
+	for (int y=6401; y<6500; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6500, m, 1})==GregorianCalendar::fixedFromGregorian({6500, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6500, m, 1})==GregorianCalendar::fixedFromGregorian({6500, m, 1})-1);
+	for (int y=6501; y<6800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6800, m, 1})==GregorianCalendar::fixedFromGregorian({6800, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6800, m, 1})==GregorianCalendar::fixedFromGregorian({6800, m, 1})-2);
+	for (int y=6801; y<6900; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6900, m, 1})==GregorianCalendar::fixedFromGregorian({6900, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({6900, m, 1})==GregorianCalendar::fixedFromGregorian({6900, m, 1})-1);
+	for (int y=6901; y<7200; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7200, m, 1})==GregorianCalendar::fixedFromGregorian({7200, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7200, m, 1})==GregorianCalendar::fixedFromGregorian({7200, m, 1})-2);
+	for (int y=7201; y<7400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7400, m, 1})==GregorianCalendar::fixedFromGregorian({7400, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7400, m, 1})==GregorianCalendar::fixedFromGregorian({7400, m, 1})-1);
+	for (int y=7401; y<7600; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7600, m, 1})==GregorianCalendar::fixedFromGregorian({7600, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7600, m, 1})==GregorianCalendar::fixedFromGregorian({7600, m, 1})-2);
+	for (int y=7601; y<7800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7800, m, 1})==GregorianCalendar::fixedFromGregorian({7800, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({7800, m, 1})==GregorianCalendar::fixedFromGregorian({7800, m, 1})-1);
+	for (int y=7801; y<8000; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8000, m, 1})==GregorianCalendar::fixedFromGregorian({8000, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8000, m, 1})==GregorianCalendar::fixedFromGregorian({8000, m, 1})-2);
+	for (int y=8001; y<8300; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8300, m, 1})==GregorianCalendar::fixedFromGregorian({8300, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8300, m, 1})==GregorianCalendar::fixedFromGregorian({8300, m, 1})-1);
+	for (int y=8301; y<8400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8400, m, 1})==GregorianCalendar::fixedFromGregorian({8400, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8400, m, 1})==GregorianCalendar::fixedFromGregorian({8400, m, 1})-2);
+	for (int y=8401; y<8700; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8700, m, 1})==GregorianCalendar::fixedFromGregorian({8700, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8700, m, 1})==GregorianCalendar::fixedFromGregorian({8700, m, 1})-1);
+	for (int y=8701; y<8800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-1);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8800, m, 1})==GregorianCalendar::fixedFromGregorian({8800, m, 1})-1);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({8800, m, 1})==GregorianCalendar::fixedFromGregorian({8800, m, 1})-2);
+	for (int y=8801; y<10000; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10000, m, 1})==GregorianCalendar::fixedFromGregorian({10000, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10000, m, 1})==GregorianCalendar::fixedFromGregorian({10000, m, 1})-3);
+	for (int y=10001; y<10100; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-3);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10100, m, 1})==GregorianCalendar::fixedFromGregorian({10100, m, 1})-3);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10100, m, 1})==GregorianCalendar::fixedFromGregorian({10100, m, 1})-2);
+	for (int y=10101; y<10400; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10400, m, 1})==GregorianCalendar::fixedFromGregorian({10400, m, 1})-2);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10400, m, 1})==GregorianCalendar::fixedFromGregorian({10400, m, 1})-3);
+	for (int y=10401; y<10500; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-3);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10500, m, 1})==GregorianCalendar::fixedFromGregorian({10500, m, 1})-3);
+	for (int m=3; m<=12; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10500, m, 1})==GregorianCalendar::fixedFromGregorian({10500, m, 1})-2);
+	for (int y=10501; y<10800; y++)
+		for (int m=1; m<=12; m++)
+			QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({y, m, 1})==GregorianCalendar::fixedFromGregorian({y, m, 1})-2);
+	for (int m=1; m<=2; m++)
+		QVERIFY(RevisedJulianCalendar::fixedFromRevisedJulian({10800, m, 1})==GregorianCalendar::fixedFromGregorian({10800, m, 1})-2);
+
 	QVERIFY(-214193==ISOCalendar::fixedFromISO({-586, 29, 7}));
 	QVERIFY( -61387==ISOCalendar::fixedFromISO({-168, 49, 3}));
 	QVERIFY(  25469==ISOCalendar::fixedFromISO({  70, 39, 3}));
@@ -1144,8 +1476,8 @@ void TestCalendars::testBalinesePawukon()
 	const QVector<int>expect2038({1, 2, 1, 3, 4, 1, 4, 7, 1, 2});
 
 	QVERIFY2(BalinesePawukonCalendar::baliPawukonFromFixed(sample2038) == expect2038,
-		 qPrintable(QString("Bali for %1 = %2").arg(QString::number(sample2038))
-			    .arg(printVec(BalinesePawukonCalendar::baliPawukonFromFixed(sample2038)))));
+		 qPrintable(QString("Bali for %1 = %2").arg(QString::number(sample2038),
+			    printVec(BalinesePawukonCalendar::baliPawukonFromFixed(sample2038)))));
 
 	QVERIFY(-214193==BalinesePawukonCalendar::baliOnOrBefore({0, 1, 1, 1, 3, 1, 1, 5, 7, 3}, -214193));
 	QVERIFY( -61387==BalinesePawukonCalendar::baliOnOrBefore({1, 2, 2, 1, 4, 5, 4, 5, 5, 2},  -61387));