Unexpected Format in Timestamp

src/PhpSpreadsheet/Document/Properties.php

@@ -172,6 +172,8 @@ private static function intOrFloatTimestamp($timestamp)
                 $timestamp = (float) $timestamp;
             } else {
                 $timestamp = preg_replace('/[.][0-9]*$/', '', $timestamp) ?? '';
+                $timestamp = preg_replace('/^(\\d{4})- (\\d)/', '$1-0$2', $timestamp) ?? '';
+                $timestamp = preg_replace('/^(\\d{4}-\\d{2})- (\\d)/', '$1-0$2', $timestamp) ?? '';
                 $timestamp = (float) (new DateTime($timestamp))->format('U');
             }
         }

src/PhpSpreadsheet/Reader/Xlsx/Properties.php

@@ -52,8 +52,8 @@ public function readCoreProperties(string $propertyData): void
 
             $this->docProps->setCreator((string) self::getArrayItem($xmlCore->xpath('dc:creator')));
             $this->docProps->setLastModifiedBy((string) self::getArrayItem($xmlCore->xpath('cp:lastModifiedBy')));
-            $this->docProps->setCreated((int) strtotime((string) self::getArrayItem($xmlCore->xpath('dcterms:created')))); //! respect xsi:type
-            $this->docProps->setModified((int) strtotime((string) self::getArrayItem($xmlCore->xpath('dcterms:modified')))); //! respect xsi:type
+            $this->docProps->setCreated((string) self::getArrayItem($xmlCore->xpath('dcterms:created'))); //! respect xsi:type
+            $this->docProps->setModified((string) self::getArrayItem($xmlCore->xpath('dcterms:modified'))); //! respect xsi:type
             $this->docProps->setTitle((string) self::getArrayItem($xmlCore->xpath('dc:title')));
             $this->docProps->setDescription((string) self::getArrayItem($xmlCore->xpath('dc:description')));
             $this->docProps->setSubject((string) self::getArrayItem($xmlCore->xpath('dc:subject')));

tests/PhpSpreadsheetTests/Reader/Xlsx/Issue2331Test.php

@@ -0,0 +1,26 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Reader\Xlsx;
+
+use DateTimeZone;
+use PhpOffice\PhpSpreadsheet\IOFactory;
+use PhpOffice\PhpSpreadsheet\Shared\Date;
+use PHPUnit\Framework\TestCase;
+
+class Issue2331Test extends TestCase
+{
+    public function testIssue2331(): void
+    {
+        // Leading space instead of 0 in month and/or day of timestamp.
+        $filename = 'tests/data/Reader/XLSX/issue.2331c.xlsx';
+        $reader = IOFactory::createReader('Xlsx');
+        $spreadsheet = $reader->load($filename);
+        $properties = $spreadsheet->getProperties();
+        $created = (string) $properties->getCreated();
+        $modified = (string) $properties->getModified();
+
+        self::assertEquals('2021-08-02', Date::formattedDateTimeFromTimestamp($created, 'Y-m-d', new DateTimeZone('UTC')));
+        self::assertEquals('2021-09-03', Date::formattedDateTimeFromTimestamp($modified, 'Y-m-d', new DateTimeZone('UTC')));
+        $spreadsheet->disconnectWorksheets();
+    }
+}