diff --git a/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php b/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php
index a272a2e..2a9d398 100644
--- a/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php
+++ b/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php
@@ -283,16 +283,16 @@ class CellValueFormatter
 
     /**
      * Returns a cell's PHP Date value, associated to the given stored nodeValue.
+     * @see ECMA-376 Part 1 - §18.17.4
      *
-     * @param string $nodeValue
-     * @return \DateTime|null The value associated with the cell or NULL if invalid date value
+     * @param string $nodeValue ISO 8601 Date string
+     * @return \DateTime|string|null The value associated with the cell or NULL if invalid date value
      */
     protected function formatDateCellValue($nodeValue)
     {
         // Mitigate thrown Exception on invalid date-time format (http://php.net/manual/en/datetime.construct.php)
         try {
-            $cellValue = new \DateTime($nodeValue);
-            return $cellValue;
+            return ($this->shouldFormatDates) ? $nodeValue : new \DateTime($nodeValue);
         } catch (\Exception $e) {
             return null;
         }
diff --git a/tests/Spout/Reader/XLSX/ReaderTest.php b/tests/Spout/Reader/XLSX/ReaderTest.php
index 02c91ed..0deb84c 100644
--- a/tests/Spout/Reader/XLSX/ReaderTest.php
+++ b/tests/Spout/Reader/XLSX/ReaderTest.php
@@ -274,6 +274,7 @@ class ReaderTest extends \PHPUnit_Framework_TestCase
         $expectedRows = [
             ['1/13/2016', '01/13/2016', '13-Jan-16', 'Wednesday January 13, 16', 'Today is 1/13/2016'],
             ['4:43:25', '04:43', '4:43', '4:43:25 AM', '4:43:25 PM'],
+            ['1976-11-22T08:30:00.000', '1976-11-22T08:30', '1582-10-15', '08:30:00', '08:30'],
         ];
         $this->assertEquals($expectedRows, $allRows);
     }
diff --git a/tests/resources/xlsx/sheet_with_dates_and_times.xlsx b/tests/resources/xlsx/sheet_with_dates_and_times.xlsx
index 769e03b..b73d65a 100644
Binary files a/tests/resources/xlsx/sheet_with_dates_and_times.xlsx and b/tests/resources/xlsx/sheet_with_dates_and_times.xlsx differ