include/tools/datetime.hxx         |    9 +
 include/tools/duration.hxx         |   72 +++++++++
 sc/inc/table.hxx                   |    8 -
 sc/source/core/data/documen3.cxx   |    3 
 sc/source/core/data/table4.cxx     |  117 +++++++++------
 tools/CppunitTest_tools_test.mk    |    1 
 tools/Library_tl.mk                |    1 
 tools/qa/cppunit/test_duration.cxx |  278 +++++++++++++++++++++++++++++++++++++
 tools/source/datetime/datetime.cxx |   38 ++---
 tools/source/datetime/duration.cxx |  256 ++++++++++++++++++++++++++++++++++
 10 files changed, 717 insertions(+), 66 deletions(-)

New commits:
commit 0770c99928fa0c4af23b06cbf694ee77ee78b836
Author:     Eike Rathke <er...@redhat.com>
AuthorDate: Sat Jun 17 01:05:48 2023 +0200
Commit:     Eike Rathke <er...@redhat.com>
CommitDate: Sat Jun 17 18:04:56 2023 +0200

    Resolves: tdf#153517 Use tools::Duration for FillSeries with (date+)time
    
    Change-Id: I18567fdac512ee786ce4b0785b01b2ae6da7450e
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153203
    Tested-by: Jenkins
    Reviewed-by: Eike Rathke <er...@redhat.com>
    (cherry picked from commit 45bee6b9a0e620758d0d4079d832d80095164b0a)
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153219

diff --git a/sc/inc/table.hxx b/sc/inc/table.hxx
index a2cc60f9d70e..0662053cb89c 100644
--- a/sc/inc/table.hxx
+++ b/sc/inc/table.hxx
@@ -715,7 +715,8 @@ public:
                                  sc::UpdatedRangeNames& rIndexes) const;
     void        Fill( SCCOL nCol1, SCROW nRow1, SCCOL nCol2, SCROW nRow2,
                         sal_uInt64 nFillCount, FillDir eFillDir, FillCmd 
eFillCmd, FillDateCmd eFillDateCmd,
-                        double nStepValue, double nMaxValue, ScProgress* 
pProgress);
+                        double nStepValue, const tools::Duration& 
rDurationStep,
+                        double nMaxValue, ScProgress* pProgress);
     OUString    GetAutoFillPreview( const ScRange& rSource, SCCOL nEndX, SCROW 
nEndY );
 
     void UpdateSelectionFunction( ScFunctionData& rData, const ScMarkData& 
rMark );
@@ -1191,13 +1192,14 @@ private:
     void        FillSeries( SCCOL nCol1, SCROW nRow1, SCCOL nCol2, SCROW nRow2,
                                 sal_uInt64 nFillCount, FillDir eFillDir, 
FillCmd eFillCmd,
                                 FillDateCmd eFillDateCmd,
-                                double nStepValue, double nMaxValue, 
sal_uInt16 nMinDigits,
+                                double nStepValue, const tools::Duration& 
rDurationStep,
+                                double nMaxValue, sal_uInt16 nMinDigits,
                                 bool bAttribs, ScProgress* pProgress,
                                 bool bSkipOverlappedCells = false,
                                 std::vector<sal_Int32>* pNonOverlappedCellIdx 
= nullptr);
     void        FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL nCol2, SCROW 
nRow2,
                                 FillCmd& rCmd, FillDateCmd& rDateCmd,
-                                double& rInc, sal_uInt16& rMinDigits,
+                                double& rInc, tools::Duration& rDuration, 
sal_uInt16& rMinDigits,
                                 ScUserListData*& rListData, sal_uInt16& 
rListIndex,
                                 bool bHasFiltered, bool& rSkipOverlappedCells,
                                 std::vector<sal_Int32>& rNonOverlappedCellIdx 
);
diff --git a/sc/source/core/data/documen3.cxx b/sc/source/core/data/documen3.cxx
index b1cf5fe81b8c..8d0d2ba9a665 100644
--- a/sc/source/core/data/documen3.cxx
+++ b/sc/source/core/data/documen3.cxx
@@ -29,6 +29,7 @@
 #include <vcl/svapp.hxx>
 #include <osl/thread.hxx>
 #include <osl/diagnose.h>
+#include <tools/duration.hxx>
 #include <document.hxx>
 #include <attrib.hxx>
 #include <table.hxx>
@@ -1171,7 +1172,7 @@ void ScDocument::Fill(SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2, ScProg
         {
             maTabs[rTab]->Fill(nCol1, nRow1, nCol2, nRow2,
                             nFillCount, eFillDir, eFillCmd, eFillDateCmd,
-                            nStepValue, nMaxValue, pProgress);
+                            nStepValue, tools::Duration(), nMaxValue, 
pProgress);
             RefreshAutoFilter(aRange.aStart.Col(), aRange.aStart.Row(), 
aRange.aEnd.Col(), aRange.aEnd.Row(), rTab);
         }
     }
diff --git a/sc/source/core/data/table4.cxx b/sc/source/core/data/table4.cxx
index 10c27f8d2c84..9c6852990efe 100644
--- a/sc/source/core/data/table4.cxx
+++ b/sc/source/core/data/table4.cxx
@@ -28,6 +28,7 @@
 #include <vcl/keycodes.hxx>
 #include <rtl/math.hxx>
 #include <unotools/charclass.hxx>
+#include <tools/duration.hxx>
 #include <osl/diagnose.h>
 
 #include <attrib.hxx>
@@ -215,32 +216,20 @@ double approxDiff( double a, double b )
     return rtl::math::round(c, -std::max(nExp, nExpArg));
 }
 
-double approxTimeDiff( double a, double b )
+double approxTypedDiff( double a, double b, bool bTime, tools::Duration& 
rDuration )
 {
-    // Scale to hours, round to "nanohours" (multiple nanoseconds), scale back.
-    // Get back 0.0416666666666667 instead of 0.041666666700621136 or
-    // 0.041666666664241347 (raw a-b) for one hour, or worse the approxDiff()
-    // 0.041666666659999997 value. Though there is no such correct value,
-    // IEEE-754 nearest values are
-    // 0.041666666666666664353702032030923874117434024810791015625
-    // (0x3FA5555555555555) and
-    // 0.04166666666666667129259593593815225176513195037841796875
-    // (0x3FA5555555555556).
-    // This works also for a diff of seconds, unless corner cases would be
-    // discovered, which would make it necessary to ditch the floating point
-    // and convert to/from time structure values instead.
-    return rtl::math::round((a - b) * 24, 9) / 24;
-}
-
-double approxTypedDiff( double a, double b, bool bTime )
-{
-    return bTime ? approxTimeDiff( a, b) : approxDiff( a, b);
+    if (bTime)
+    {
+        rDuration = tools::Duration(a - b);
+        return rDuration.GetInDays();
+    }
+    return approxDiff( a, b);
 }
 }
 
 void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL nCol2, SCROW nRow2,
                             FillCmd& rCmd, FillDateCmd& rDateCmd,
-                            double& rInc, sal_uInt16& rMinDigits,
+                            double& rInc, tools::Duration& rDuration, 
sal_uInt16& rMinDigits,
                             ScUserListData*& rListData, sal_uInt16& rListIndex,
                             bool bHasFiltered, bool& rSkipOverlappedCells,
                             std::vector<sal_Int32>& rNonOverlappedCellIdx)
@@ -248,6 +237,7 @@ void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
     OSL_ENSURE( nCol1==nCol2 || nRow1==nRow2, "FillAnalyse: invalid range" );
 
     rInc = 0.0;
+    rDuration = tools::Duration();
     rMinDigits = 0;
     rListData = nullptr;
     rCmd = FILL_SIMPLE;
@@ -413,6 +403,7 @@ void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
                 }
                 else if (nValueCount >= 2)
                 {
+                    tools::Duration aDuration;
                     for (SCSIZE i = 1; i < nValueCount && bVal; i++)
                     {
                         aPrevCell = aCurrCell;
@@ -421,11 +412,16 @@ void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, 
SCCOL nCol2, SCROW nRow2,
                         aCurrCell = GetCellValue(nColCurr, nRowCurr);
                         if (aCurrCell.getType() == CELLTYPE_VALUE)
                         {
+                            const bool bTime = (nCurrCellFormatType == 
SvNumFormatType::TIME ||
+                                    nCurrCellFormatType == 
SvNumFormatType::DATETIME);
                             double nDiff = 
approxTypedDiff(aCurrCell.getDouble(), aPrevCell.getDouble(),
-                                    (nCurrCellFormatType == 
SvNumFormatType::TIME ||
-                                     nCurrCellFormatType == 
SvNumFormatType::DATETIME));
+                                    bTime, aDuration);
                             if (i == 1)
+                            {
                                 rInc = nDiff;
+                                if (bTime)
+                                    rDuration = aDuration;
+                            }
                             if (!::rtl::math::approxEqual(nDiff, rInc, 13))
                                 bVal = false;
                             else if ((aCurrCell.getDouble() == 0.0 || 
aCurrCell.getDouble() == 1.0)
@@ -645,9 +641,10 @@ void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
         {
             if (nCount > 1)
             {
+                tools::Duration aDuration;
                 double nVal1 = aFirstCell.getDouble();
                 double nVal2 = GetValue(nCol+nAddX, nRow+nAddY);
-                rInc = approxTypedDiff( nVal2, nVal1, bTime);
+                rInc = approxTypedDiff( nVal2, nVal1, bTime, aDuration);
                 nCol = sal::static_int_cast<SCCOL>( nCol + nAddX );
                 nRow = sal::static_int_cast<SCROW>( nRow + nAddY );
                 bool bVal = true;
@@ -657,7 +654,7 @@ void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
                     if (aCell.getType() == CELLTYPE_VALUE)
                     {
                         nVal2 = aCell.getDouble();
-                        double nDiff = approxTypedDiff( nVal2, nVal1, bTime);
+                        double nDiff = approxTypedDiff( nVal2, nVal1, bTime, 
aDuration);
                         if ( !::rtl::math::approxEqual( nDiff, rInc, 13 ) )
                             bVal = false;
                         else if ((nVal2 == 0.0 || nVal2 == 1.0) &&
@@ -670,6 +667,8 @@ void ScTable::FillAnalyse( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
                         bVal = false;
                     nCol = sal::static_int_cast<SCCOL>( nCol + nAddX );
                     nRow = sal::static_int_cast<SCROW>( nRow + nAddY );
+                    if (bVal && bTime)
+                        rDuration = aDuration;
                 }
                 if (bVal)
                     rCmd = FILL_LINEAR;
@@ -1092,6 +1091,7 @@ void ScTable::FillAuto( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
         FillCmd eFillCmd;
         FillDateCmd eDateCmd = {};
         double nInc;
+        tools::Duration aDurationInc;
         sal_uInt16 nMinDigits;
         ScUserListData* pListData = nullptr;
         sal_uInt16 nListIndex;
@@ -1100,12 +1100,12 @@ void ScTable::FillAuto( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
         if (bVertical)
             FillAnalyse(static_cast<SCCOL>(nCol),nRow1,
                     static_cast<SCCOL>(nCol),nRow2, eFillCmd,eDateCmd,
-                    nInc, nMinDigits, pListData, nListIndex,
+                    nInc, aDurationInc, nMinDigits, pListData, nListIndex,
                     bHasFiltered, bSkipOverlappedCells, aNonOverlappedCellIdx);
         else
             FillAnalyse(nCol1,static_cast<SCROW>(nRow),
                     nCol2,static_cast<SCROW>(nRow), eFillCmd,eDateCmd,
-                    nInc, nMinDigits, pListData, nListIndex,
+                    nInc, aDurationInc, nMinDigits, pListData, nListIndex,
                     bHasFiltered, bSkipOverlappedCells, aNonOverlappedCellIdx);
 
         if (pListData)
@@ -1214,17 +1214,20 @@ void ScTable::FillAuto( SCCOL nCol1, SCROW nRow1, SCCOL 
nCol2, SCROW nRow2,
         else
         {
             if (!bPositive)
+            {
                 nInc = -nInc;
+                aDurationInc = -aDurationInc;
+            }
             double nEndVal = (nInc>=0.0) ? MAXDOUBLE : -MAXDOUBLE;
             if (bVertical)
                 FillSeries( static_cast<SCCOL>(nCol), nRow1,
                         static_cast<SCCOL>(nCol), nRow2, nFillCount, eFillDir,
-                        eFillCmd, eDateCmd, nInc, nEndVal, nMinDigits, false,
+                        eFillCmd, eDateCmd, nInc, aDurationInc, nEndVal, 
nMinDigits, false,
                         pProgress, bSkipOverlappedCells, 
&aNonOverlappedCellIdx);
             else
                 FillSeries( nCol1, static_cast<SCROW>(nRow), nCol2,
                         static_cast<SCROW>(nRow), nFillCount, eFillDir,
-                        eFillCmd, eDateCmd, nInc, nEndVal, nMinDigits, false,
+                        eFillCmd, eDateCmd, nInc, aDurationInc, nEndVal, 
nMinDigits, false,
                         pProgress, bSkipOverlappedCells, 
&aNonOverlappedCellIdx);
             if (pProgress)
                 nProgress = pProgress->GetState();
@@ -1375,6 +1378,7 @@ OUString ScTable::GetAutoFillPreview( const ScRange& 
rSource, SCCOL nEndX, SCROW
         FillCmd eFillCmd;
         FillDateCmd eDateCmd;
         double nInc;
+        tools::Duration aDurationInc;
         sal_uInt16 nMinDigits;
         ScUserListData* pListData = nullptr;
         sal_uInt16 nListIndex;
@@ -1385,7 +1389,7 @@ OUString ScTable::GetAutoFillPreview( const ScRange& 
rSource, SCCOL nEndX, SCROW
         //       after FillAnalyse / FillSeries fully handle them.
         // Now FillAnalyse called as if there are filtered rows, so it will 
work in the old way.
         FillAnalyse(nCol1, nRow1, nCol2, nRow2, eFillCmd, eDateCmd,
-                    nInc, nMinDigits, pListData, nListIndex,
+                    nInc, aDurationInc, nMinDigits, pListData, nListIndex,
                     true, bSkipOverlappedCells, aNonOverlappedCellIdx);
 
         if ( pListData )                            // user defined list
@@ -1530,9 +1534,18 @@ OUString ScTable::GetAutoFillPreview( const ScRange& 
rSource, SCCOL nEndX, SCROW
                 nStart = 0.0;
             if ( eFillCmd == FILL_LINEAR )
             {
-                double nAdd = nInc;
-                bValueOk = ( SubTotal::SafeMult( nAdd, 
static_cast<double>(nIndex) ) &&
-                             SubTotal::SafePlus( nStart, nAdd ) );
+                if (aDurationInc)
+                {
+                    bool bOverflow;
+                    tools::Duration aDuration( aDurationInc.Mult( nIndex, 
bOverflow));
+                    bValueOk = SubTotal::SafePlus( nStart, 
aDuration.GetInDays()) && !bOverflow;
+                }
+                else
+                {
+                    double nAdd = nInc;
+                    bValueOk = ( SubTotal::SafeMult( nAdd, 
static_cast<double>(nIndex) ) &&
+                                 SubTotal::SafePlus( nStart, nAdd ) );
+                }
             }
             else        // date
             {
@@ -2153,7 +2166,8 @@ inline bool isOverflow( const double& rVal, const double& 
rMax, const double& rS
 
 void ScTable::FillSeries( SCCOL nCol1, SCROW nRow1, SCCOL nCol2, SCROW nRow2,
                     sal_uInt64 nFillCount, FillDir eFillDir, FillCmd eFillCmd, 
FillDateCmd eFillDateCmd,
-                    double nStepValue, double nMaxValue, sal_uInt16 
nArgMinDigits,
+                    double nStepValue, const tools::Duration& rDurationStep,
+                    double nMaxValue, sal_uInt16 nArgMinDigits,
                     bool bAttribs, ScProgress* pProgress,
                     bool bSkipOverlappedCells, std::vector<sal_Int32>* 
pNonOverlappedCellIdx )
 {
@@ -2420,10 +2434,18 @@ void ScTable::FillSeries( SCCOL nCol1, SCROW nRow1, 
SCCOL nCol2, SCROW nRow2,
                                         //  use multiplication instead of 
repeated addition
                                         //  to avoid accumulating rounding 
errors
                                         nVal = nStartVal;
-                                        double nAdd = nStepValue;
-                                        if ( !SubTotal::SafeMult( nAdd, 
static_cast<double>(++nIndex) ) ||
-                                                !SubTotal::SafePlus( nVal, 
nAdd ) )
-                                            bError = true;
+                                        if (rDurationStep)
+                                        {
+                                            tools::Duration aDuration( 
rDurationStep.Mult( ++nIndex, bError));
+                                            bError |= !SubTotal::SafePlus( 
nVal, aDuration.GetInDays());
+                                        }
+                                        else
+                                        {
+                                            double nAdd = nStepValue;
+                                            if ( !SubTotal::SafeMult( nAdd, 
static_cast<double>(++nIndex) ) ||
+                                                    !SubTotal::SafePlus( nVal, 
nAdd ) )
+                                                bError = true;
+                                        }
                                     }
                                     break;
                                 case FILL_GROWTH:
@@ -2525,10 +2547,18 @@ void ScTable::FillSeries( SCCOL nCol1, SCROW nRow1, 
SCCOL nCol2, SCROW nRow2,
                                             //  use multiplication instead of 
repeated addition
                                             //  to avoid accumulating rounding 
errors
                                             nVal = nStartVal;
-                                            double nAdd = nStepValue;
-                                            if ( !SubTotal::SafeMult( nAdd, 
static_cast<double>(++nIndex) ) ||
-                                                    !SubTotal::SafePlus( nVal, 
nAdd ) )
-                                                bError = true;
+                                            if (rDurationStep)
+                                            {
+                                                tools::Duration aDuration( 
rDurationStep.Mult( ++nIndex, bError));
+                                                bError |= !SubTotal::SafePlus( 
nVal, aDuration.GetInDays());
+                                            }
+                                            else
+                                            {
+                                                double nAdd = nStepValue;
+                                                if ( !SubTotal::SafeMult( 
nAdd, static_cast<double>(++nIndex) ) ||
+                                                        !SubTotal::SafePlus( 
nVal, nAdd ) )
+                                                    bError = true;
+                                            }
                                         }
                                         break;
                                     case FILL_GROWTH:
@@ -2598,13 +2628,14 @@ void ScTable::FillSeries( SCCOL nCol1, SCROW nRow1, 
SCCOL nCol2, SCROW nRow2,
 
 void ScTable::Fill( SCCOL nCol1, SCROW nRow1, SCCOL nCol2, SCROW nRow2,
                     sal_uInt64 nFillCount, FillDir eFillDir, FillCmd eFillCmd, 
FillDateCmd eFillDateCmd,
-                    double nStepValue, double nMaxValue, ScProgress* pProgress)
+                    double nStepValue, const tools::Duration& rDurationStep,
+                    double nMaxValue, ScProgress* pProgress)
 {
     if (eFillCmd == FILL_AUTO)
         FillAuto(nCol1, nRow1, nCol2, nRow2, nFillCount, eFillDir, pProgress);
     else
         FillSeries(nCol1, nRow1, nCol2, nRow2, nFillCount, eFillDir,
-                    eFillCmd, eFillDateCmd, nStepValue, nMaxValue, 0, true, 
pProgress);
+                    eFillCmd, eFillDateCmd, nStepValue, rDurationStep, 
nMaxValue, 0, true, pProgress);
 }
 
 void ScTable::AutoFormatArea(SCCOL nStartCol, SCROW nStartRow, SCCOL nEndCol, 
SCROW nEndRow,
commit 69f757a4bb32a844f7754f6fc6b9970557297528
Author:     Eike Rathke <er...@redhat.com>
AuthorDate: Sat Jun 17 00:57:42 2023 +0200
Commit:     Eike Rathke <er...@redhat.com>
CommitDate: Sat Jun 17 18:04:45 2023 +0200

    Related: tdf#153517 Introduce class tools::Duration
    
    Change-Id: I73ea6e162c73382ba470a306ce2852dbff3d1314
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153202
    Reviewed-by: Eike Rathke <er...@redhat.com>
    Tested-by: Jenkins
    (cherry picked from commit eac63ab120a181a1dff6317ee3d223327080e992)
    Reviewed-on: https://gerrit.libreoffice.org/c/core/+/153218

diff --git a/include/tools/datetime.hxx b/include/tools/datetime.hxx
index dd435e3994ba..2194711dc208 100644
--- a/include/tools/datetime.hxx
+++ b/include/tools/datetime.hxx
@@ -26,6 +26,11 @@
 
 #include <iomanip>
 
+namespace tools
+{
+class Duration;
+}
+
 class SAL_WARN_UNUSED TOOLS_DLLPUBLIC DateTime : public Date, public 
tools::Time
 {
 public:
@@ -83,6 +88,8 @@ public:
     void            AddTime( double fTimeInDays );
     DateTime&       operator +=( const tools::Time& rTime );
     DateTime&       operator -=( const tools::Time& rTime );
+    /** Duration can be negative, so adding it will subtract its value. */
+    DateTime&       operator +=( const tools::Duration& rDuration );
 private:
     void            NormalizeTimeRemainderAndApply( tools::Time& rTime );
 public:
@@ -97,6 +104,8 @@ public:
     TOOLS_DLLPUBLIC friend double   operator -( const DateTime& rDateTime1, 
const DateTime& rDateTime2 );
     TOOLS_DLLPUBLIC friend sal_Int64 operator -( const DateTime& rDateTime, 
const Date& rDate )
                         { return static_cast<const Date&>(rDateTime) - rDate; }
+    /** Duration can be negative, so adding it will subtract its value. */
+    TOOLS_DLLPUBLIC friend DateTime operator +( const DateTime& rDateTime, 
const tools::Duration& rDuration );
 
     DateTime&       operator =( const DateTime& rDateTime );
     DateTime&       operator =( const css::util::DateTime& rUDateTime );
diff --git a/include/tools/duration.hxx b/include/tools/duration.hxx
new file mode 100644
index 000000000000..83b9d12a77b3
--- /dev/null
+++ b/include/tools/duration.hxx
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; 
fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <tools/time.hxx>
+
+class DateTime;
+
+namespace tools
+{
+/** Duration in days and time. Can be negative in which case days is 0 and time
+    is negative or both days and time are negative.
+*/
+class SAL_WARN_UNUSED TOOLS_DLLPUBLIC Duration
+{
+public:
+    Duration() {}
+
+    /** Assumes that DateTime are normalized and there are no Time out-of-range
+        field values. */
+    Duration(const ::DateTime& rStart, const ::DateTime& rEnd);
+
+    /** Time can be a limited duration as well. We don't cater for out-of-range
+        minutes and seconds values here though. */
+    Duration(const Time& rStart, const Time& rEnd);
+
+    /** Difference in days, like DateTime()-DateTime(). */
+    explicit Duration(double fTimeInDays);
+
+    bool IsNegative() const { return mnDays < 0 || maTime.GetTime() < 0; }
+    sal_Int32 GetDays() const { return mnDays; }
+    const Time& GetTime() const { return maTime; }
+    double GetInDays() const { return static_cast<double>(GetDays()) + 
GetTime().GetTimeInDays(); }
+
+    /** Whether a duration is set. */
+    operator bool() const { return maTime.GetTime() != 0 || mnDays != 0; }
+
+    /** Unary minus. */
+    Duration operator-() const;
+
+    /** Add a duration to this instance. */
+    Duration& Add(const Duration& rDuration, bool& rbOverflow);
+
+    /** Get multiple of duration. */
+    Duration Mult(sal_Int32 nMult, bool& rbOverflow) const;
+
+private:
+    /** Internal days and Time values. */
+    Duration(sal_Int32 nDays, sal_Int64 nTime);
+
+    /** Prerequisite: mnDays is already correctly set and absolute value of
+        nanoseconds less than one day. */
+    void ApplyTime(sal_Int64 nNS);
+
+    /** Prerequisite: mnDays is already correctly set and Time hour values
+        are adjusted. */
+    void SetTimeDiff(const Time& rStart, const Time& rEnd);
+
+private:
+    Time maTime = Time(0);
+    sal_Int32 mnDays = 0;
+};
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s 
cinkeys+=0=break: */
diff --git a/tools/CppunitTest_tools_test.mk b/tools/CppunitTest_tools_test.mk
index 9cf6c671fcef..d27f8c3efa58 100644
--- a/tools/CppunitTest_tools_test.mk
+++ b/tools/CppunitTest_tools_test.mk
@@ -17,6 +17,7 @@ $(eval $(call 
gb_CppunitTest_add_exception_objects,tools_test, \
     tools/qa/cppunit/test_bigint \
     tools/qa/cppunit/test_date \
     tools/qa/cppunit/test_time \
+    tools/qa/cppunit/test_duration \
     tools/qa/cppunit/test_fract \
     tools/qa/cppunit/test_inetmime \
     tools/qa/cppunit/test_json_writer \
diff --git a/tools/Library_tl.mk b/tools/Library_tl.mk
index bccbf95a2a01..8269e6ae98bf 100644
--- a/tools/Library_tl.mk
+++ b/tools/Library_tl.mk
@@ -45,6 +45,7 @@ $(eval $(call gb_Library_use_libraries,tl,\
 $(eval $(call gb_Library_add_exception_objects,tl,\
     tools/source/datetime/datetime \
     tools/source/datetime/datetimeutils \
+    tools/source/datetime/duration \
     tools/source/datetime/systemdatetime \
     tools/source/datetime/tdate \
     tools/source/datetime/ttime \
diff --git a/tools/qa/cppunit/test_duration.cxx 
b/tools/qa/cppunit/test_duration.cxx
new file mode 100644
index 000000000000..0f5a4e002219
--- /dev/null
+++ b/tools/qa/cppunit/test_duration.cxx
@@ -0,0 +1,278 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <cppunit/TestFixture.h>
+#include <cppunit/extensions/HelperMacros.h>
+
+#include <tools/duration.hxx>
+#include <tools/datetime.hxx>
+
+namespace tools
+{
+class DurationTest : public CppUnit::TestFixture
+{
+public:
+    void testDuration();
+
+    CPPUNIT_TEST_SUITE(DurationTest);
+    CPPUNIT_TEST(testDuration);
+    CPPUNIT_TEST_SUITE_END();
+};
+
+void DurationTest::testDuration()
+{
+    {
+        const Duration aD(Time(0), Time(12, 0, 0));
+        CPPUNIT_ASSERT_EQUAL(0.5, aD.GetInDays());
+    }
+    {
+        const Duration aD(Time(24, 0, 0), Time(12, 0, 0));
+        CPPUNIT_ASSERT_EQUAL(-0.5, aD.GetInDays());
+    }
+    {
+        const DateTime aS(Date(23, 11, 1999), Time(6, 0, 0));
+        const DateTime aE(Date(24, 11, 1999), Time(18, 0, 0));
+        const Duration aD(aS, aE);
+        CPPUNIT_ASSERT_EQUAL(1.5, aD.GetInDays());
+        DateTime aDT1(aS);
+        const DateTime aDT2 = aDT1 + aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT2);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT1);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(26, 11, 1999), Time(6, 0, 0)), 
aDT1);
+    }
+    {
+        const DateTime aS(Date(23, 11, 1999), Time(18, 0, 0));
+        const DateTime aE(Date(24, 11, 1999), Time(6, 0, 0));
+        const Duration aD(aS, aE);
+        CPPUNIT_ASSERT_EQUAL(0.5, aD.GetInDays());
+        DateTime aDT1(aS);
+        const DateTime aDT2 = aDT1 + aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT2);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT1);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(24, 11, 1999), Time(18, 0, 0)), 
aDT1);
+    }
+    {
+        const DateTime aS(Date(24, 11, 1999), Time(18, 0, 0));
+        const DateTime aE(Date(23, 11, 1999), Time(6, 0, 0));
+        const Duration aD(aS, aE);
+        CPPUNIT_ASSERT_EQUAL(-1.5, aD.GetInDays());
+        DateTime aDT1(aS);
+        const DateTime aDT2 = aDT1 + aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT2);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT1);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(21, 11, 1999), Time(18, 0, 0)), 
aDT1);
+    }
+    {
+        const DateTime aS(Date(24, 11, 1999), Time(6, 0, 0));
+        const DateTime aE(Date(23, 11, 1999), Time(18, 0, 0));
+        const Duration aD(aS, aE);
+        CPPUNIT_ASSERT_EQUAL(-0.5, aD.GetInDays());
+        DateTime aDT1(aS);
+        const DateTime aDT2 = aDT1 + aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT2);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(aE, aDT1);
+        aDT1 += aD;
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(23, 11, 1999), Time(6, 0, 0)), 
aDT1);
+    }
+    {
+        const Duration aD(1.5);
+        CPPUNIT_ASSERT_EQUAL(1.5, aD.GetInDays());
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(24, 11, 1999), Time(18, 0, 0)),
+                             DateTime(Date(23, 11, 1999), Time(6, 0, 0)) + aD);
+    }
+    {
+        const Duration aD(-1.5);
+        CPPUNIT_ASSERT_EQUAL(-1.5, aD.GetInDays());
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(23, 11, 1999), Time(6, 0, 0)),
+                             DateTime(Date(24, 11, 1999), Time(18, 0, 0)) + 
aD);
+    }
+    {
+        const Duration aD(-1.5);
+        const Duration aN = -aD;
+        CPPUNIT_ASSERT_EQUAL(1.5, aN.GetInDays());
+    }
+    { // Add()
+        const DateTime aS(Date(23, 11, 1999), Time(0, 0, 0));
+        const DateTime aE(Date(23, 11, 1999), Time(1, 23, 45));
+        const Duration aD(aS, aE);
+        Duration aV = aD;
+        bool bOverflow = true;
+        aV.Add(aD, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(23, 11, 1999), Time(2, 47, 30)),
+                             DateTime(Date(23, 11, 1999), Time(0, 0, 0)) + aV);
+        for (int i = 0; i < 20; ++i)
+            aV.Add(aD, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(24, 11, 1999), Time(6, 42, 30)),
+                             DateTime(Date(23, 11, 1999), Time(0, 0, 0)) + aV);
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_Int32>(1), aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(6), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(42), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(30), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT(aV.GetTime().GetTime() > 0);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(1.27951388888889, aV.GetInDays(), 1E-14);
+        // Negative duration.
+        const Duration aN(aE, aS);
+        aV = aN;
+        aV.Add(aN, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(22, 11, 1999), Time(21, 12, 30)),
+                             DateTime(Date(23, 11, 1999), Time(0, 0, 0)) + aV);
+        for (int i = 0; i < 20; ++i)
+            aV.Add(aN, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(21, 11, 1999), Time(17, 17, 30)),
+                             DateTime(Date(23, 11, 1999), Time(0, 0, 0)) + aV);
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_Int32>(-1), aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(6), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(42), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(30), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT(aV.GetTime().GetTime() < 0);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(-1.27951388888889, aV.GetInDays(), 1E-14);
+    }
+    { // Mult()
+        const DateTime aS(Date(23, 11, 1999), Time(0, 0, 0));
+        const DateTime aE(Date(23, 11, 1999), Time(1, 23, 45));
+        const Duration aD(aS, aE);
+        bool bOverflow = true;
+        Duration aV = aD.Mult(22, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(24, 11, 1999), Time(6, 42, 30)),
+                             DateTime(Date(23, 11, 1999), Time(0, 0, 0)) + aV);
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_Int32>(1), aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(6), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(42), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(30), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT(aV.GetTime().GetTime() > 0);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(1.27951388888889, aV.GetInDays(), 1E-14);
+        // Negative duration.
+        const Duration aN(aE, aS);
+        bOverflow = true;
+        aV = aN.Mult(22, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_EQUAL(DateTime(Date(21, 11, 1999), Time(17, 17, 30)),
+                             DateTime(Date(23, 11, 1999), Time(0, 0, 0)) + aV);
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_Int32>(-1), aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(6), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(42), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(30), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT(aV.GetTime().GetTime() < 0);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(-1.27951388888889, aV.GetInDays(), 1E-14);
+    }
+    { // Mult() including days.
+        const Duration aD(1.5);
+        bool bOverflow = true;
+        Duration aV = aD.Mult(10, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(15.0, aV.GetInDays(), 0.0);
+    }
+    { // Mult() including days.
+        const Duration aD(-1.5);
+        bool bOverflow = true;
+        Duration aV = aD.Mult(10, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(-15.0, aV.GetInDays(), 0.0);
+    }
+    { // Mult() including days.
+        const Duration aD(1.5);
+        bool bOverflow = true;
+        Duration aV = aD.Mult(-10, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(-15.0, aV.GetInDays(), 0.0);
+    }
+    { // Mult() including days.
+        const Duration aD(-1.5);
+        bool bOverflow = true;
+        Duration aV = aD.Mult(-10, bOverflow);
+        CPPUNIT_ASSERT(!bOverflow);
+        CPPUNIT_ASSERT_DOUBLES_EQUAL(15.0, aV.GetInDays(), 0.0);
+    }
+    { // Mult() with overflow.
+        const Duration aD(SAL_MAX_INT32);
+        bool bOverflow = false;
+        Duration aV = aD.Mult(2, bOverflow);
+        CPPUNIT_ASSERT(bOverflow);
+        CPPUNIT_ASSERT_EQUAL(SAL_MAX_INT32, aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(23), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt32>(Time::nanoSecPerSec - 1),
+                             aV.GetTime().GetNanoSec());
+    }
+    { // Mult() with overflow.
+        const Duration aD(SAL_MIN_INT32);
+        bool bOverflow = false;
+        Duration aV = aD.Mult(2, bOverflow);
+        CPPUNIT_ASSERT(bOverflow);
+        CPPUNIT_ASSERT_EQUAL(SAL_MIN_INT32, aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(23), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt32>(Time::nanoSecPerSec - 1),
+                             aV.GetTime().GetNanoSec());
+    }
+    { // Mult() with overflow.
+        const Duration aD(SAL_MAX_INT32);
+        bool bOverflow = false;
+        Duration aV = aD.Mult(-2, bOverflow);
+        CPPUNIT_ASSERT(bOverflow);
+        CPPUNIT_ASSERT_EQUAL(SAL_MIN_INT32, aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(23), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt32>(Time::nanoSecPerSec - 1),
+                             aV.GetTime().GetNanoSec());
+    }
+    { // Mult() with overflow.
+        const Duration aD(SAL_MIN_INT32);
+        bool bOverflow = false;
+        Duration aV = aD.Mult(-2, bOverflow);
+        CPPUNIT_ASSERT(bOverflow);
+        CPPUNIT_ASSERT_EQUAL(SAL_MAX_INT32, aV.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(23), 
aV.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(59), 
aV.GetTime().GetSec());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt32>(Time::nanoSecPerSec - 1),
+                             aV.GetTime().GetNanoSec());
+    }
+    { // Inaccurate double yielding exact duration.
+        const Time aS(15, 0, 0);
+        const Time aE(16, 0, 0);
+        const Duration aD(aE.GetTimeInDays() - aS.GetTimeInDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_Int32>(0), aD.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(1), 
aD.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(0), 
aD.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(0), 
aD.GetTime().GetSec());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt32>(0), 
aD.GetTime().GetNanoSec());
+    }
+    { // Inaccurate double yielding exact duration, negative.
+        const Time aS(15, 0, 0);
+        const Time aE(16, 0, 0);
+        const Duration aD(aS.GetTimeInDays() - aE.GetTimeInDays());
+        CPPUNIT_ASSERT(aD.IsNegative());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_Int32>(0), aD.GetDays());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(1), 
aD.GetTime().GetHour());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(0), 
aD.GetTime().GetMin());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt16>(0), 
aD.GetTime().GetSec());
+        CPPUNIT_ASSERT_EQUAL(static_cast<sal_uInt32>(0), 
aD.GetTime().GetNanoSec());
+    }
+}
+
+CPPUNIT_TEST_SUITE_REGISTRATION(DurationTest);
+}
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s 
cinkeys+=0=break: */
diff --git a/tools/source/datetime/datetime.cxx 
b/tools/source/datetime/datetime.cxx
index 47dc0555bc87..ec2c53673b17 100644
--- a/tools/source/datetime/datetime.cxx
+++ b/tools/source/datetime/datetime.cxx
@@ -17,6 +17,7 @@
  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  */
 #include <tools/datetime.hxx>
+#include <tools/duration.hxx>
 #include <rtl/math.hxx>
 #include <sal/log.hxx>
 
@@ -136,6 +137,13 @@ DateTime& DateTime::operator -=( const tools::Time& rTime )
     return *this;
 }
 
+DateTime& DateTime::operator +=( const tools::Duration& rDuration )
+{
+    AddDays(rDuration.GetDays());
+    operator+=(rDuration.GetTime());
+    return *this;
+}
+
 DateTime operator +( const DateTime& rDateTime, sal_Int32 nDays )
 {
     DateTime aDateTime( rDateTime );
@@ -164,27 +172,19 @@ DateTime operator -( const DateTime& rDateTime, const 
tools::Time& rTime )
     return aDateTime;
 }
 
+DateTime operator +( const DateTime& rDateTime, const tools::Duration& 
rDuration )
+{
+    DateTime aDateTime(rDateTime);
+    aDateTime.AddDays( rDuration.GetDays());
+    aDateTime += rDuration.GetTime();
+    return aDateTime;
+}
+
 void DateTime::AddTime( double fTimeInDays )
 {
-    double fInt, fFrac;
-    if ( fTimeInDays < 0.0 )
-    {
-        fInt = ::rtl::math::approxCeil( fTimeInDays );
-        fFrac = fInt <= fTimeInDays ? 0.0 : fTimeInDays - fInt;
-    }
-    else
-    {
-        fInt = ::rtl::math::approxFloor( fTimeInDays );
-        fFrac = fInt >= fTimeInDays ? 0.0 : fTimeInDays - fInt;
-    }
-    AddDays( sal_Int32(fInt) );     // full days
-    if ( fFrac )
-    {
-        tools::Time aTime(0);  // default ctor calls system time, we don't 
need that
-        fFrac *= ::tools::Time::nanoSecPerDay;   // time expressed in 
nanoseconds
-        aTime.MakeTimeFromNS( static_cast<sal_Int64>(fFrac) );    // method 
handles negative ns
-        operator+=( aTime );
-    }
+    // Use Duration to diminish floating point accuracy errors.
+    tools::Duration aDuration(fTimeInDays);
+    operator+=(aDuration);
 }
 
 DateTime operator +( const DateTime& rDateTime, double fTimeInDays )
diff --git a/tools/source/datetime/duration.cxx 
b/tools/source/datetime/duration.cxx
new file mode 100644
index 000000000000..07f79929177f
--- /dev/null
+++ b/tools/source/datetime/duration.cxx
@@ -0,0 +1,256 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; 
fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#include <tools/duration.hxx>
+#include <tools/datetime.hxx>
+#include <rtl/math.hxx>
+#include <o3tl/safeint.hxx>
+#include <cmath>
+
+namespace tools
+{
+Duration::Duration(const ::DateTime& rStart, const ::DateTime& rEnd)
+    : mnDays(static_cast<const Date&>(rEnd) - static_cast<const Date&>(rStart))
+{
+    SetTimeDiff(rStart, rEnd);
+}
+
+Duration::Duration(const Time& rStart, const Time& rEnd)
+{
+    const sal_uInt16 nStartHour = rStart.GetHour();
+    const sal_uInt16 nEndHour = rEnd.GetHour();
+    if (nStartHour >= 24 || nEndHour >= 24)
+    {
+        Time aEnd(rEnd);
+        if (nEndHour >= 24)
+        {
+            mnDays = (nEndHour / 24) * (aEnd.GetTime() < 0 ? -1 : 1);
+            aEnd.SetHour(nEndHour % 24);
+        }
+        Time aStart(rStart);
+        if (nStartHour >= 24)
+        {
+            mnDays -= (nStartHour / 24) * (aStart.GetTime() < 0 ? -1 : 1);
+            aStart.SetHour(nStartHour % 24);
+        }
+        SetTimeDiff(aStart, aEnd);
+    }
+    else
+    {
+        SetTimeDiff(rStart, rEnd);
+    }
+}
+
+Duration::Duration(double fTimeInDays)
+{
+    double fInt, fFrac;
+    if (fTimeInDays < 0.0)
+    {
+        fInt = ::rtl::math::approxCeil(fTimeInDays);
+        fFrac = fInt <= fTimeInDays ? 0.0 : fTimeInDays - fInt;
+    }
+    else
+    {
+        fInt = ::rtl::math::approxFloor(fTimeInDays);
+        fFrac = fInt >= fTimeInDays ? 0.0 : fTimeInDays - fInt;
+    }
+    mnDays = static_cast<sal_Int32>(fInt);
+    if (fFrac)
+    {
+        fFrac *= Time::nanoSecPerDay;
+        fFrac = ::rtl::math::approxFloor(fFrac);
+        sal_Int64 nNS = static_cast<sal_Int64>(fFrac);
+        // Round by 1 nanosecond if it's just 1 off to a second, i.e.
+        // 0999999999 or 0000000001. This could be losened to rounding by 2 or
+        // such if necessary.
+        const sal_Int64 nN = nNS % Time::nanoSecPerSec;
+        if (std::abs(nN) == 1)
+            nNS -= (nNS < 0) ? -1 : 1;
+        else if (std::abs(nN) == Time::nanoSecPerSec - 1)
+        {
+            nNS += (nNS < 0) ? -1 : 1;
+            if (std::abs(nNS) >= Time::nanoSecPerDay)
+            {
+                mnDays += nNS / Time::nanoSecPerDay;
+                nNS %= Time::nanoSecPerDay;
+            }
+        }
+        maTime.MakeTimeFromNS(nNS);
+        assert(mnDays == 0 || maTime.GetTime() == 0 || (mnDays < 0) == (nNS < 
0));
+    }
+}
+
+Duration::Duration(sal_Int32 nDays, sal_Int64 nTime)
+    : maTime(nTime)
+    , mnDays(nDays)
+{
+}
+
+void Duration::ApplyTime(sal_Int64 nNS)
+{
+    if (mnDays > 0 && nNS < 0)
+    {
+        --mnDays;
+        nNS = Time::nanoSecPerDay + nNS;
+    }
+    else if (mnDays < 0 && nNS > 0)
+    {
+        ++mnDays;
+        nNS = -Time::nanoSecPerDay + nNS;
+    }
+    maTime.MakeTimeFromNS(nNS);
+    assert(mnDays == 0 || maTime.GetTime() == 0 || (mnDays < 0) == (nNS < 0));
+}
+
+void Duration::SetTimeDiff(const Time& rStart, const Time& rEnd)
+{
+    const sal_Int64 nNS = rEnd.GetNSFromTime() - rStart.GetNSFromTime();
+    ApplyTime(nNS);
+}
+
+Duration Duration::operator-() const
+{
+    Duration aD(-mnDays, -maTime.GetTime());
+    return aD;
+}
+
+Duration& Duration::Add(const Duration& rDuration, bool& rbOverflow)
+{
+    rbOverflow = o3tl::checked_add(mnDays, rDuration.mnDays, mnDays);
+    // Duration is always normalized, time values >= 24h don't occur.
+    sal_Int64 nNS = maTime.GetNSFromTime() + rDuration.maTime.GetNSFromTime();
+    if (nNS < -Time::nanoSecPerDay)
+    {
+        rbOverflow |= o3tl::checked_sub(mnDays, sal_Int32(1), mnDays);
+        nNS += Time::nanoSecPerDay;
+    }
+    else if (nNS > Time::nanoSecPerDay)
+    {
+        rbOverflow |= o3tl::checked_add(mnDays, sal_Int32(1), mnDays);
+        nNS -= Time::nanoSecPerDay;
+    }
+    ApplyTime(nNS);
+    return *this;
+}
+
+Duration Duration::Mult(sal_Int32 nMult, bool& rbOverflow) const
+{
+    // First try a simple calculation in nanoseconds.
+    bool bBadNS = false;
+    sal_Int64 nNS;
+    sal_Int64 nDays;
+    if (o3tl::checked_multiply(static_cast<sal_Int64>(mnDays), 
static_cast<sal_Int64>(nMult), nDays)
+        || o3tl::checked_multiply(nDays, Time::nanoSecPerDay, nDays)
+        || o3tl::checked_multiply(maTime.GetNSFromTime(), 
static_cast<sal_Int64>(nMult), nNS)
+        || o3tl::checked_add(nDays, nNS, nNS))
+    {
+        bBadNS = rbOverflow = true;
+    }
+    else
+    {
+        const sal_Int64 nD = nNS / Time::nanoSecPerDay;
+        if (nD < SAL_MIN_INT32 || SAL_MAX_INT32 < nD)
+            rbOverflow = true;
+        else
+        {
+            rbOverflow = false;
+            nNS -= nD * Time::nanoSecPerDay;
+            Duration aD(static_cast<sal_Int32>(nD), 0);
+            aD.ApplyTime(nNS);
+            return aD;
+        }
+    }
+    if (bBadNS)
+    {
+        // Simple calculation in overall nanoseconds overflew, try with
+        // individual components.
+        const sal_uInt64 nMult64 = (nMult < 0) ? -nMult : nMult;
+        do
+        {
+            rbOverflow = true;
+            sal_uInt64 nN;
+            if 
(o3tl::checked_multiply(static_cast<sal_uInt64>(maTime.GetNanoSec()), nMult64, 
nN))
+                break;
+            sal_uInt64 nS;
+            if 
(o3tl::checked_multiply(static_cast<sal_uInt64>(maTime.GetSec()), nMult64, nS))
+                break;
+            sal_uInt64 nM;
+            if 
(o3tl::checked_multiply(static_cast<sal_uInt64>(maTime.GetMin()), nMult64, nM))
+                break;
+            sal_uInt64 nH;
+            if 
(o3tl::checked_multiply(static_cast<sal_uInt64>(maTime.GetHour()), nMult64, nH))
+                break;
+            sal_uInt64 nD;
+            if (o3tl::checked_multiply(static_cast<sal_uInt64>(mnDays < 0 ? 
-mnDays : mnDays),
+                                       nMult64, nD))
+                break;
+            if (nN > Time::nanoSecPerSec)
+            {
+                const sal_uInt64 nC = nN / Time::nanoSecPerSec;
+                if (o3tl::checked_add(nS, nC, nS))
+                    break;
+                nN -= nC * Time::nanoSecPerSec;
+            }
+            if (nS > Time::secondPerMinute)
+            {
+                const sal_uInt64 nC = nS / Time::secondPerMinute;
+                if (o3tl::checked_add(nM, nC, nM))
+                    break;
+                nS -= nC * Time::secondPerMinute;
+            }
+            if (nM > Time::minutePerHour)
+            {
+                const sal_uInt64 nC = nM / Time::minutePerHour;
+                if (o3tl::checked_add(nH, nC, nH))
+                    break;
+                nM -= nC * Time::minutePerHour;
+            }
+            if (nH > Time::hourPerDay)
+            {
+                const sal_uInt64 nC = nH / Time::hourPerDay;
+                if (o3tl::checked_add(nD, nC, nD))
+                    break;
+                nH -= nC * Time::hourPerDay;
+            }
+            if (IsNegative() ? (static_cast<sal_uInt64>(SAL_MAX_INT32) + 1) < 
nD
+                                   || -static_cast<sal_Int64>(nD) < 
SAL_MIN_INT32
+                             : SAL_MAX_INT32 < nD)
+                break;
+
+            rbOverflow = false;
+            Time aTime(nH, nM, nS, nN);
+            if (IsNegative() == (nMult < 0))
+            {
+                Duration aD(nD, aTime.GetTime());
+                return aD;
+            }
+            else
+            {
+                Duration aD(-static_cast<sal_Int64>(nD), -aTime.GetTime());
+                return aD;
+            }
+        } while (false);
+    }
+    assert(rbOverflow);
+    if (IsNegative() == (nMult < 0))
+    {
+        Duration aD(SAL_MAX_INT32, 0);
+        aD.ApplyTime(Time::nanoSecPerDay - 1);
+        return aD;
+    }
+    else
+    {
+        Duration aD(SAL_MIN_INT32, 0);
+        aD.ApplyTime(-(Time::nanoSecPerDay - 1));
+        return aD;
+    }
+}
+};
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s 
cinkeys+=0=break: */

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