From 7ed96e0be15ef292bc05283b3f6122fc0f28968b Mon Sep 17 00:00:00 2001
From: Alban Duval <aduval@profideo.com>
Date: Mon, 25 May 2020 21:33:48 +0200
Subject: [PATCH] Calcualtion - DATEDIF - fix result for Y & YM units (#1466)

Bugfix for negative results and too small results

2000-02-02 => 2001-02-01
 > DATEDIF with Y unit: 0 year (returned -1 before fix)
 > DATEDIF with YM unit: 11 months (returned -1 before fix)
---
 src/PhpSpreadsheet/Calculation/DateTime.php | 30 +++++----------------
 tests/data/Calculation/DateTime/DATEDIF.php | 14 +++++++++-
 2 files changed, 19 insertions(+), 25 deletions(-)

diff --git a/src/PhpSpreadsheet/Calculation/DateTime.php b/src/PhpSpreadsheet/Calculation/DateTime.php
index d08ab543..19860794 100644
--- a/src/PhpSpreadsheet/Calculation/DateTime.php
+++ b/src/PhpSpreadsheet/Calculation/DateTime.php
@@ -668,30 +668,19 @@ class DateTime
         $endMonths = $PHPEndDateObject->format('n');
         $endYears = $PHPEndDateObject->format('Y');
 
+        $PHPDiffDateObject = $PHPEndDateObject->diff($PHPStartDateObject);
+
         switch ($unit) {
             case 'D':
                 $retVal = (int) $difference;
 
                 break;
             case 'M':
-                $retVal = (int) ($endMonths - $startMonths) + ((int) ($endYears - $startYears) * 12);
-                //    We're only interested in full months
-                if ($endDays < $startDays) {
-                    --$retVal;
-                }
+                $retVal = (int) 12 * $PHPDiffDateObject->format('%y') + $PHPDiffDateObject->format('%m');
 
                 break;
             case 'Y':
-                $retVal = (int) ($endYears - $startYears);
-                //    We're only interested in full months
-                if ($endMonths < $startMonths) {
-                    --$retVal;
-                } elseif (($endMonths == $startMonths) && ($endDays < $startDays)) {
-                    // Remove start month
-                    --$retVal;
-                    // Remove end month
-                    --$retVal;
-                }
+                $retVal = (int) $PHPDiffDateObject->format('%y');
 
                 break;
             case 'MD':
@@ -701,19 +690,12 @@ class DateTime
                     $adjustDays = $PHPEndDateObject->format('j');
                     $retVal += ($adjustDays - $startDays);
                 } else {
-                    $retVal = $endDays - $startDays;
+                    $retVal = (int) $PHPDiffDateObject->format('%d');
                 }
 
                 break;
             case 'YM':
-                $retVal = (int) ($endMonths - $startMonths);
-                if ($retVal < 0) {
-                    $retVal += 12;
-                }
-                //    We're only interested in full months
-                if ($endDays < $startDays) {
-                    --$retVal;
-                }
+                $retVal = (int) $PHPDiffDateObject->format('%m');
 
                 break;
             case 'YD':
diff --git a/tests/data/Calculation/DateTime/DATEDIF.php b/tests/data/Calculation/DateTime/DATEDIF.php
index d113d3aa..a6d2d761 100644
--- a/tests/data/Calculation/DateTime/DATEDIF.php
+++ b/tests/data/Calculation/DateTime/DATEDIF.php
@@ -393,6 +393,10 @@ return [
         1,
         '19-12-1960', '26-01-2012', 'YM',
     ],
+    [
+        11,
+        '19-12-1960', '26-11-1962', 'YM',
+    ],
     [
         38,
         '19-12-1960', '26-01-2012', 'YD',
@@ -402,7 +406,15 @@ return [
         '19-12-1960', '26-01-2012', 'MD',
     ],
     [
-        50,
+        0,
+        '19-12-1960', '12-12-1961', 'Y',
+    ],
+    [
+        1,
+        '19-12-1960', '12-12-1962', 'Y',
+    ],
+    [
+        51,
         '19-12-1960', '12-12-2012', 'Y',
     ],
     [