Date::Normalize: handle day 0 and empty date

* Empty date (initialized with Date::EMPTY == all 0) stays empty.
* Day 0 is normalized to the last day of the previous month.
* Day 0 AND month 0 is also normalized to the last day of the previous month
  (and not the last day of the previous-1 month).
* Before,
  * all day 0 cases weren't handled at all and day 0 stayed day 0, which
    doesn't make sense in a Normalize() context
  * empty date wasn't detected and resulted in nonsense date -0001-12-00

Change-Id: Ib12ff7694e1adb17724af038a266f6f284285f36

1 files changed, 16 insertions, 0 deletions

diff --git a/tools/source/datetime/tdate.cxx b/tools/source/datetime/tdate.cxx
index 9815716ebe3f..3dd8f68b3ced 100644
--- a/tools/source/datetime/tdate.cxx
+++ b/tools/source/datetime/tdate.cxx
@@ -493,6 +493,18 @@ bool Date::Normalize( sal_uInt16 & rDay, sal_uInt16 & rMonth, sal_Int16 & rYear
     if (IsValidDate( rDay, rMonth, rYear))
         return false;
 
+    if (rDay == 0 && rMonth == 0 && rYear == 0)
+        return false;   // empty date
+
+    if (rDay == 0)
+    {
+        if (rMonth == 0)
+            ;   // nothing, handled below
+        else
+            --rMonth;
+        // Last day of month is determined at the end.
+    }
+
     if (rMonth > 12)
     {
         rYear += rMonth / 12;
@@ -550,6 +562,10 @@ bool Date::Normalize( sal_uInt16 & rDay, sal_uInt16 & rMonth, sal_Int16 & rYear
             }
         }
     }
+
+    if (rDay == 0)
+        rDay = ImplDaysInMonth( rMonth, rYear);
+
     return true;
 }