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>

1 files changed, 2 insertions, 2 deletions

diff --git a/include/vcl/field.hxx b/include/vcl/field.hxx
index d07624e8a92c..d277a0a55b59 100644
--- a/include/vcl/field.hxx
+++ b/include/vcl/field.hxx
@@ -336,12 +336,12 @@ public:
     void                    SetEmptyDate();
     bool                    IsEmptyDate() const;
 
-    void                    ResetLastDate() { maLastDate = Date( 0, 0, 0 ); }
+    void                    ResetLastDate() { maLastDate = Date( Date::EMPTY ); }
 
     static void             ExpandCentury( Date& rDate );
     static void             ExpandCentury( Date& rDate, sal_uInt16 nTwoDigitYearStart );
 
-    static Date             GetInvalidDate() { return Date( 0, 0, 0 ); }
+    static Date             GetInvalidDate() { return Date( Date::EMPTY ); }
 
     /** enables or disables the enforcement of valid values