Resolves: tdf#100452 class Date full (BCE,CE) proleptic Gregorian calendar

... implementing signed years with year 0 gap.
Date(31,12,-1) last day BCE
Date(1,1,1) first day CE

New class Date member functions:
* AddYears(sal_Int16) to be used instead of
aDate.SetYear(aDate.GetYear()+sal_Int16) to handle year 0 gap.
* convenience GetNextYear() to be used insted of GetYear()+1
* convenience GetPrevYear() to be used insted of GetYear()-1
* AddMonths(sal_Int32)
* operator=(const css::util::Date&)

New class DateTime member functions:
* operator=(const css::util::DateTime&)

Made some conversion ctors explicit, specifically Date(sal_Int32)

Adapted hopefully all places that used a sal_uInt16 year to use
sal_Int16 where appropriate.

Eliminated some quirks in date handling found on the fly.

Added era handling to i18npool icu calendar setting interface, which
missing was responsible for 0001-01-01 entered in Calc being set as
-0001-01-01, hence subtracting one day resulted in -0002-12-31.

Change-Id: I77b39fba9599ebd5067d7864f6c9ebe01f6f578f
Reviewed-on: https://gerrit.libreoffice.org/27049
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Jenkins <ci@libreoffice.org>

2 files changed, 15 insertions, 7 deletions

diff --git a/xmloff/source/core/xmluconv.cxx b/xmloff/source/core/xmluconv.cxx
index 1f2fe2446f38..fa34a3006f6b 100644
--- a/xmloff/source/core/xmluconv.cxx
+++ b/xmloff/source/core/xmluconv.cxx
@@ -375,21 +375,29 @@ void SvXMLUnitConverter::convertDateTime( OUStringBuffer& rBuffer,
             aDate += 1;
         }
     }
-    sal_uInt16 nTemp = aDate.GetYear();
-    if (nTemp < 1000)
+    sal_Int16 nTempYear = aDate.GetYear();
+    assert(nTempYear != 0);
+    if (nTempYear < 0)
+    {
+        rBuffer.append( '-');
+        nTempYear = -nTempYear;
+    }
+    if (nTempYear < 1000)
         rBuffer.append( '0');
-    if (nTemp < 100)
+    if (nTempYear < 100)
         rBuffer.append( '0');
-    if (nTemp < 10)
+    if (nTempYear < 10)
         rBuffer.append( '0');
-    rBuffer.append( sal_Int32( nTemp));
+    rBuffer.append( sal_Int32( nTempYear));
     rBuffer.append( '-');
-    nTemp = aDate.GetMonth();
+    sal_uInt16 nTemp = aDate.GetMonth();
+    assert(1 <= nTemp && nTemp <= 12);
     if (nTemp < 10)
         rBuffer.append( '0');
     rBuffer.append( sal_Int32( nTemp));
     rBuffer.append( '-');
     nTemp = aDate.GetDay();
+    assert(1 <= nTemp && nTemp <= 31);
     if (nTemp < 10)
         rBuffer.append( '0');
     rBuffer.append( sal_Int32( nTemp));
diff --git a/xmloff/source/text/txtlists.cxx b/xmloff/source/text/txtlists.cxx
index 3fd31e514b4b..09c62c7f742c 100644
--- a/xmloff/source/text/txtlists.cxx
+++ b/xmloff/source/text/txtlists.cxx
@@ -225,7 +225,7 @@ OUString XMLTextListsHelper::GenerateNewListId() const
     {
         // Value of xml:id in element <text:list> has to be a valid ID type (#i92478#)
         sal_Int64 n = ::tools::Time( ::tools::Time::SYSTEM ).GetTime();
-        n += Date( Date::SYSTEM ).GetDate();
+        n += Date( Date::SYSTEM ).GetDateUnsigned();
         n += comphelper::rng::uniform_int_distribution(0, std::numeric_limits<int>::max());
         // Value of xml:id in element <text:list> has to be a valid ID type (#i92478#)
         sTmpStr += OUString::number( n );