diff --git a/src/Spout/Reader/Wrapper/SimpleXMLElement.php b/src/Spout/Reader/Wrapper/SimpleXMLElement.php
index 4892aca..0e3d758 100644
--- a/src/Spout/Reader/Wrapper/SimpleXMLElement.php
+++ b/src/Spout/Reader/Wrapper/SimpleXMLElement.php
@@ -151,6 +151,22 @@ class SimpleXMLElement
         return $doesElementExist ? $this->wrapSimpleXMLElement($realElement) : null;
     }
 
+    /**
+     * Returns the immediate children.
+     *
+     * @return array The children
+     */
+    public function children()
+    {
+        $children = [];
+
+        foreach ($this->simpleXMLElement->children() as $child) {
+            $children[] = $this->wrapSimpleXMLElement($child);
+        }
+
+        return $children;
+    }
+
     /**
      * @return string
      */
diff --git a/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php b/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php
index 79f92e7..3c417ca 100644
--- a/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php
+++ b/src/Spout/Reader/XLSX/Helper/CellValueFormatter.php
@@ -25,19 +25,35 @@ class CellValueFormatter
 
     /** Definition of XML attributes used to parse data */
     const XML_ATTRIBUTE_TYPE = 't';
+    const XML_ATTRIBUTE_STYLE_ID = 's';
+
+    /** Constants used for date formatting */
+    const NUM_DAYS_FROM_JAN_1_1900_TO_JAN_1_1970 = 25569; // actually 25567 but accommodating for an Excel bug with some bisextile years
+    const NUM_SECONDS_IN_ONE_DAY = 86400;
+
+    /**
+     * February 29th, 1900 is NOT a leap year but Excel thinks it is...
+     * @see https://en.wikipedia.org/wiki/Year_1900_problem#Microsoft_Excel
+     */
+    const ERRONEOUS_EXCEL_LEAP_YEAR_DAY = 60;
 
     /** @var SharedStringsHelper Helper to work with shared strings */
     protected $sharedStringsHelper;
 
+    /** @var StyleHelper Helper to work with styles */
+    protected $styleHelper;
+
     /** @var \Box\Spout\Common\Escaper\XLSX Used to unescape XML data */
     protected $escaper;
 
     /**
      * @param SharedStringsHelper $sharedStringsHelper Helper to work with shared strings
+     * @param StyleHelper $styleHelper Helper to work with styles
      */
-    public function __construct($sharedStringsHelper)
+    public function __construct($sharedStringsHelper, $styleHelper)
     {
         $this->sharedStringsHelper = $sharedStringsHelper;
+        $this->styleHelper = $styleHelper;
 
         /** @noinspection PhpUnnecessaryFullyQualifiedNameInspection */
         $this->escaper = new \Box\Spout\Common\Escaper\XLSX();
@@ -53,6 +69,7 @@ class CellValueFormatter
     {
         // Default cell type is "n"
         $cellType = $node->getAttribute(self::XML_ATTRIBUTE_TYPE) ?: self::CELL_TYPE_NUMERIC;
+        $cellStyleId = intval($node->getAttribute(self::XML_ATTRIBUTE_STYLE_ID));
         $vNodeValue = $this->getVNodeValue($node);
 
         if (($vNodeValue === '') && ($cellType !== self::CELL_TYPE_INLINE_STRING)) {
@@ -69,7 +86,7 @@ class CellValueFormatter
             case self::CELL_TYPE_BOOLEAN:
                 return $this->formatBooleanCellValue($vNodeValue);
             case self::CELL_TYPE_NUMERIC:
-                return $this->formatNumericCellValue($vNodeValue);
+                return $this->formatNumericCellValue($vNodeValue, $cellStyleId);
             case self::CELL_TYPE_DATE:
                 return $this->formatDateCellValue($vNodeValue);
             default:
@@ -138,14 +155,49 @@ class CellValueFormatter
 
     /**
      * Returns the cell Numeric value from string of nodeValue.
+     * The value can also represent a timestamp and a DateTime will be returned.
      *
      * @param string $nodeValue
-     * @return int|float The value associated with the cell
+     * @param int $cellStyleId 0 being the default style
+     * @return int|float|\DateTime|null The value associated with the cell
      */
-    protected function formatNumericCellValue($nodeValue)
+    protected function formatNumericCellValue($nodeValue, $cellStyleId)
     {
-        $cellValue = is_int($nodeValue) ? intval($nodeValue) : floatval($nodeValue);
-        return $cellValue;
+        // Numeric values can represent numbers as well as timestamps.
+        // We need to look at the style of the cell to determine whether it is one or the other.
+        $shouldFormatAsDate = $this->styleHelper->shouldFormatNumericValueAsDate($cellStyleId);
+
+        if ($shouldFormatAsDate) {
+            return $this->formatExcelTimestampValue(floatval($nodeValue));
+        } else {
+            return is_int($nodeValue) ? intval($nodeValue) : floatval($nodeValue);
+        }
+    }
+
+    /**
+     * Returns a cell's PHP Date value, associated to the given timestamp.
+     * NOTE: The timestamp is a float representing the number of days since January 1st, 1900.
+     *
+     * @param float $nodeValue
+     * @return \DateTime|null The value associated with the cell or NULL if invalid date value
+     */
+    protected function formatExcelTimestampValue($nodeValue)
+    {
+        $numDaysSince1970Jan1 = $nodeValue - self::NUM_DAYS_FROM_JAN_1_1900_TO_JAN_1_1970;
+
+        // Fix for the erroneous leap year in Excel
+        if ($nodeValue < self::ERRONEOUS_EXCEL_LEAP_YEAR_DAY) {
+            $numDaysSince1970Jan1++;
+        }
+
+        $unixTimestamp = round($numDaysSince1970Jan1 * self::NUM_SECONDS_IN_ONE_DAY);
+
+        try {
+            $cellValue = (new \DateTime())->setTimestamp($unixTimestamp);
+            return $cellValue;
+        } catch (\Exception $e) {
+            return null;
+        }
     }
 
     /**
diff --git a/src/Spout/Reader/XLSX/Helper/StyleHelper.php b/src/Spout/Reader/XLSX/Helper/StyleHelper.php
new file mode 100644
index 0000000..52d1844
--- /dev/null
+++ b/src/Spout/Reader/XLSX/Helper/StyleHelper.php
@@ -0,0 +1,224 @@
+<?php
+
+namespace Box\Spout\Reader\XLSX\Helper;
+
+use Box\Spout\Reader\Wrapper\SimpleXMLElement;
+use Box\Spout\Reader\Wrapper\XMLReader;
+
+/**
+ * Class StyleHelper
+ * This class provides helper functions related to XLSX styles
+ *
+ * @package Box\Spout\Reader\XLSX\Helper
+ */
+class StyleHelper
+{
+    /** Paths of XML files relative to the XLSX file root */
+    const STYLES_XML_FILE_PATH = 'xl/styles.xml';
+
+    /** Nodes used to find relevant information in the styles XML file */
+    const XML_NODE_NUM_FMTS = 'numFmts';
+    const XML_NODE_NUM_FMT = 'numFmt';
+    const XML_NODE_CELL_XFS = 'cellXfs';
+    const XML_NODE_XF = 'xf';
+
+    /** Attributes used to find relevant information in the styles XML file */
+    const XML_ATTRIBUTE_NUM_FMT_ID = 'numFmtId';
+    const XML_ATTRIBUTE_FORMAT_CODE = 'formatCode';
+    const XML_ATTRIBUTE_APPLY_NUMBER_FORMAT = 'applyNumberFormat';
+
+    /** By convention, default style ID is 0 */
+    const DEFAULT_STYLE_ID = 0;
+
+    /** @var string Path of the XLSX file being read */
+    protected $filePath;
+
+    /** @var array Array containing a mapping NUM_FMT_ID => FORMAT_CODE */
+    protected $customNumberFormats;
+
+    /** @var array Array containing a mapping STYLE_ID => [STYLE_ATTRIBUTES] */
+    protected $stylesAttributes;
+
+    /**
+     * @param string $filePath Path of the XLSX file being read
+     */
+    public function __construct($filePath)
+    {
+        $this->filePath = $filePath;
+    }
+
+    /**
+     * Reads the styles.xml file and extract the relevant information from the file.
+     *
+     * @return void
+     */
+    protected function extractRelevantInfo()
+    {
+        $this->customNumberFormats = [];
+        $this->stylesAttributes = [];
+
+        $stylesXmlFilePath = $this->filePath .'#' . self::STYLES_XML_FILE_PATH;
+        $xmlReader = new XMLReader();
+
+        if ($xmlReader->open('zip://' . $stylesXmlFilePath)) {
+            while ($xmlReader->read()) {
+                if ($xmlReader->isPositionedOnStartingNode(self::XML_NODE_NUM_FMTS)) {
+                    $numFmtsNode = new SimpleXMLElement($xmlReader->readOuterXml());
+                    $this->extractNumberFormats($numFmtsNode);
+
+                } else if ($xmlReader->isPositionedOnStartingNode(self::XML_NODE_CELL_XFS)) {
+                    $cellXfsNode = new SimpleXMLElement($xmlReader->readOuterXml());
+                    $this->extractStyleAttributes($cellXfsNode);
+                }
+            }
+
+            $xmlReader->close();
+        }
+    }
+
+    /**
+     * Extracts number formats from the "numFmt" nodes.
+     * For simplicity, the styles attributes are kept in memory. This is possible thanks
+     * to the reuse of formats. So 1 million cells should not use 1 million formats.
+     *
+     * @param SimpleXMLElement $numFmtsNode The "numFmts" node
+     * @return void
+     */
+    protected function extractNumberFormats($numFmtsNode)
+    {
+        foreach ($numFmtsNode->children() as $numFmtNode) {
+            $numFmtId = intval($numFmtNode->getAttribute(self::XML_ATTRIBUTE_NUM_FMT_ID));
+            $formatCode = $numFmtNode->getAttribute(self::XML_ATTRIBUTE_FORMAT_CODE);
+            $this->customNumberFormats[$numFmtId] = $formatCode;
+        }
+    }
+
+    /**
+     * Extracts style attributes from the "xf" nodes, inside the "cellXfs" section.
+     * For simplicity, the styles attributes are kept in memory. This is possible thanks
+     * to the reuse of styles. So 1 million cells should not use 1 million styles.
+     *
+     * @param SimpleXMLElement $cellXfsNode The "cellXfs" node
+     * @return void
+     */
+    protected function extractStyleAttributes($cellXfsNode)
+    {
+        foreach ($cellXfsNode->children() as $xfNode) {
+            $this->stylesAttributes[] = [
+                self::XML_ATTRIBUTE_NUM_FMT_ID => intval($xfNode->getAttribute(self::XML_ATTRIBUTE_NUM_FMT_ID)),
+                self::XML_ATTRIBUTE_APPLY_NUMBER_FORMAT => !!($xfNode->getAttribute(self::XML_ATTRIBUTE_APPLY_NUMBER_FORMAT)),
+            ];
+        }
+    }
+
+    /**
+     * @return array The custom number formats
+     */
+    protected function getCustomNumberFormats()
+    {
+        if (!isset($this->customNumberFormats)) {
+            $this->extractRelevantInfo();
+        }
+
+        return $this->customNumberFormats;
+    }
+
+    /**
+     * @return array The styles attributes
+     */
+    protected function getStylesAttributes()
+    {
+        if (!isset($this->stylesAttributes)) {
+            $this->extractRelevantInfo();
+        }
+
+        return $this->stylesAttributes;
+    }
+
+    /**
+     * Returns whether the style with the given ID should consider
+     * numeric values as timestamps and format the cell as a date.
+     *
+     * @param int $styleId Zero-based style ID
+     * @return bool Whether the cell with the given cell should display a date instead of a numeric value
+     */
+    public function shouldFormatNumericValueAsDate($styleId)
+    {
+        $stylesAttributes = $this->getStylesAttributes();
+
+        // Default style (0) does not format numeric values as timestamps. Only custom styles do.
+        // Also if the style ID does not exist in the styles.xml file, format as numeric value.
+        if ($styleId === self::DEFAULT_STYLE_ID || !array_key_exists($styleId, $stylesAttributes)) {
+            return false;
+        }
+
+        $styleAttributes = $stylesAttributes[$styleId];
+
+        $applyNumberFormat = $styleAttributes[self::XML_ATTRIBUTE_APPLY_NUMBER_FORMAT];
+        if (!$applyNumberFormat) {
+            return false;
+        }
+
+        $numFmtId = $styleAttributes[self::XML_ATTRIBUTE_NUM_FMT_ID];
+        return $this->doesNumFmtIdIndicateDate($numFmtId);
+    }
+
+    /**
+     * @param int $numFmtId
+     * @return bool Whether the number format ID indicates that the number is a timestamp
+     */
+    protected function doesNumFmtIdIndicateDate($numFmtId)
+    {
+        return (
+            $this->isNumFmtIdBuiltInDateFormat($numFmtId) ||
+            $this->isNumFmtIdCustomDateFormat($numFmtId)
+        );
+    }
+
+    /**
+     * @param int $numFmtId
+     * @return bool Whether the number format ID indicates that the number is a timestamp
+     */
+    protected function isNumFmtIdBuiltInDateFormat($numFmtId)
+    {
+        $builtInDateFormatIds = [14, 15, 16, 17, 18, 19, 20, 21, 22, 45, 46, 47];
+        return in_array($numFmtId, $builtInDateFormatIds);
+    }
+
+    /**
+     * @param int $numFmtId
+     * @return bool Whether the number format ID indicates that the number is a timestamp
+     */
+    protected function isNumFmtIdCustomDateFormat($numFmtId)
+    {
+        $customNumberFormats = $this->getCustomNumberFormats();
+
+        if (!array_key_exists($numFmtId, $customNumberFormats)) {
+            return false;
+        }
+
+        $customNumberFormat = $customNumberFormats[$numFmtId];
+
+        // Remove extra formatting (what's between [ ], the brackets should not be preceded by a "\")
+        $pattern = '((?<!\\\)\[.+?(?<!\\\)\])';
+        $customNumberFormat = preg_replace($pattern, '', $customNumberFormat);
+
+        // custom date formats contain specific characters to represent the date:
+        // e - yy - m - d - h - s
+        // and all of their variants (yyyy - mm - dd...)
+        $dateFormatCharacters = ['e', 'yy', 'm', 'd', 'h', 's'];
+
+        $hasFoundDateFormatCharacter = false;
+        foreach ($dateFormatCharacters as $dateFormatCharacter) {
+            // character not preceded by "\"
+            $pattern = '/(?<!\\\)' . $dateFormatCharacter . '/';
+
+            if (preg_match($pattern, $customNumberFormat)) {
+                $hasFoundDateFormatCharacter = true;
+                break;
+            }
+        }
+
+        return $hasFoundDateFormatCharacter;
+    }
+}
diff --git a/src/Spout/Reader/XLSX/RowIterator.php b/src/Spout/Reader/XLSX/RowIterator.php
index c9066c1..d1913bd 100644
--- a/src/Spout/Reader/XLSX/RowIterator.php
+++ b/src/Spout/Reader/XLSX/RowIterator.php
@@ -8,6 +8,7 @@ use Box\Spout\Reader\IteratorInterface;
 use Box\Spout\Reader\Wrapper\XMLReader;
 use Box\Spout\Reader\XLSX\Helper\CellHelper;
 use Box\Spout\Reader\XLSX\Helper\CellValueFormatter;
+use Box\Spout\Reader\XLSX\Helper\StyleHelper;
 
 /**
  * Class RowIterator
@@ -39,6 +40,9 @@ class RowIterator implements IteratorInterface
     /** @var Helper\CellValueFormatter Helper to format cell values */
     protected $cellValueFormatter;
 
+    /** @var Helper\StyleHelper $styleHelper Helper to work with styles */
+    protected $styleHelper;
+
     /** @var int Number of read rows */
     protected $numReadRows = 0;
 
@@ -62,7 +66,9 @@ class RowIterator implements IteratorInterface
         $this->sheetDataXMLFilePath = $this->normalizeSheetDataXMLFilePath($sheetDataXMLFilePath);
 
         $this->xmlReader = new XMLReader();
-        $this->cellValueFormatter = new CellValueFormatter($sharedStringsHelper);
+
+        $this->styleHelper = new StyleHelper($filePath);
+        $this->cellValueFormatter = new CellValueFormatter($sharedStringsHelper, $this->styleHelper);
     }
 
     /**
diff --git a/tests/Spout/Reader/XLSX/Helper/StyleHelperTest.php b/tests/Spout/Reader/XLSX/Helper/StyleHelperTest.php
new file mode 100644
index 0000000..3b8edff
--- /dev/null
+++ b/tests/Spout/Reader/XLSX/Helper/StyleHelperTest.php
@@ -0,0 +1,134 @@
+<?php
+
+namespace Box\Spout\Reader\XLSX\Helper;
+
+/**
+ * Class StyleHelperTest
+ *
+ * @package Box\Spout\Reader\XLSX\Helper
+ */
+class StyleHelperTest extends \PHPUnit_Framework_TestCase
+{
+
+    /**
+     * @param array $styleAttributes
+     * @param array|void $customNumberFormats
+     * @return StyleHelper
+     */
+    private function getStyleHelperMock($styleAttributes, $customNumberFormats = [])
+    {
+        /** @var StyleHelper $styleHelper */
+        $styleHelper = $this->getMockBuilder('\Box\Spout\Reader\XLSX\Helper\StyleHelper')
+                            ->setMethods(['getCustomNumberFormats', 'getStylesAttributes'])
+                            ->disableOriginalConstructor()
+                            ->getMock();
+
+        $styleHelper->method('getStylesAttributes')->willReturn($styleAttributes);
+        $styleHelper->method('getCustomNumberFormats')->willReturn($customNumberFormats);
+
+        return $styleHelper;
+    }
+
+    /**
+     * @return void
+     */
+    public function testShouldFormatNumericValueAsDateWithDefaultStyle()
+    {
+        $styleHelper = $this->getStyleHelperMock([]);
+        $shouldFormatAsDate = $styleHelper->shouldFormatNumericValueAsDate(0);
+        $this->assertFalse($shouldFormatAsDate);
+    }
+
+    /**
+     * @return void
+     */
+    public function testShouldFormatNumericValueAsDateWhenStyleIdNotListed()
+    {
+        $styleHelper = $this->getStyleHelperMock([['applyNumberFormat' => true]]);
+        $shouldFormatAsDate = $styleHelper->shouldFormatNumericValueAsDate(1);
+        $this->assertFalse($shouldFormatAsDate);
+    }
+
+    /**
+     * @return void
+     */
+    public function testShouldFormatNumericValueAsDateWhenShouldNotApplyNumberFormat()
+    {
+        $styleHelper = $this->getStyleHelperMock([[], ['applyNumberFormat' => false]]);
+        $shouldFormatAsDate = $styleHelper->shouldFormatNumericValueAsDate(1);
+        $this->assertFalse($shouldFormatAsDate);
+    }
+
+    /**
+     * @return void
+     */
+    public function testShouldFormatNumericValueAsDateWithBuiltinDateFormats()
+    {
+        $builtinNumFmtIdsForDate = [14, 15, 16, 17, 18, 19, 20, 21, 22, 45, 46, 47];
+
+        foreach ($builtinNumFmtIdsForDate as $builtinNumFmtIdForDate) {
+            $styleHelper = $this->getStyleHelperMock([[], ['applyNumberFormat' => true, 'numFmtId' => $builtinNumFmtIdForDate]]);
+            $shouldFormatAsDate = $styleHelper->shouldFormatNumericValueAsDate(1);
+
+            $this->assertTrue($shouldFormatAsDate);
+        }
+    }
+
+    /**
+     * @return void
+     */
+    public function testShouldFormatNumericValueAsDateWhenCustomNumberFormatNotFound()
+    {
+        $styleHelper = $this->getStyleHelperMock([[], ['applyNumberFormat' => true, 'numFmtId' => 165]], [166 => []]);
+        $shouldFormatAsDate = $styleHelper->shouldFormatNumericValueAsDate(1);
+
+        $this->assertFalse($shouldFormatAsDate);
+    }
+
+    /**
+     * @return array
+     */
+    public function dataProviderForCustomDateFormats()
+    {
+        return [
+            // number format, expectedResult
+            ['[$-409]dddd\,\ mmmm\ d\,\ yy', true],
+            ['[$-409]d\-mmm\-yy;@', true],
+            ['[$-409]d\-mmm\-yyyy;@', true],
+            ['mm/dd/yy;@', true],
+            ['[$-F800]dddd\,\ mmmm\ dd\,\ yyyy', true],
+            ['m/d;@', true],
+            ['m/d/yy;@', true],
+            ['[$-409]d\-mmm;@', true],
+            ['[$-409]dd\-mmm\-yy;@', true],
+            ['[$-409]mmm\-yy;@', true],
+            ['[$-409]mmmm\-yy;@', true],
+            ['[$-409]mmmm\ d\,\ yyyy;@', true],
+            ['[$-409]m/d/yy\ h:mm\ AM/PM;@', true],
+            ['m/d/yy\ h:mm;@', true],
+            ['[$-409]mmmmm;@', true],
+            ['[$-409]mmmmm\-yy;@', true],
+            ['m/d/yyyy;@', true],
+            ['[$-409]m/d/yy\--h:mm;@', true],
+            ['GENERAL', false],
+            ['\ma\yb\e', false],
+            ['[Red]foo;', false],
+        ];
+    }
+
+    /**
+     * @dataProvider dataProviderForCustomDateFormats
+     *
+     * @param string $numberFormat
+     * @param bool $expectedResult
+     * @return void
+     */
+    public function testShouldFormatNumericValueAsDateWithCustomDateFormats($numberFormat, $expectedResult)
+    {
+        $numFmtId = 165;
+        $styleHelper = $this->getStyleHelperMock([[], ['applyNumberFormat' => true, 'numFmtId' => $numFmtId]], [$numFmtId => $numberFormat]);
+        $shouldFormatAsDate = $styleHelper->shouldFormatNumericValueAsDate(1);
+
+        $this->assertEquals($expectedResult, $shouldFormatAsDate);
+    }
+}
diff --git a/tests/Spout/Reader/XLSX/ReaderTest.php b/tests/Spout/Reader/XLSX/ReaderTest.php
index eb42b84..c774749 100644
--- a/tests/Spout/Reader/XLSX/ReaderTest.php
+++ b/tests/Spout/Reader/XLSX/ReaderTest.php
@@ -113,6 +113,52 @@ class ReaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($expectedRows, $allRows);
     }
 
+    /**
+     * @return void
+     */
+    public function testReadShouldSupportNumericTimestampFormattedDifferentlyAsDate()
+    {
+        // make sure dates are always created with the same timezone
+        date_default_timezone_set('UTC');
+
+        $allRows = $this->getAllRowsForFile('sheet_with_same_numeric_value_date_formatted_differently.xlsx');
+
+        $expectedDate = \DateTime::createFromFormat('Y-m-d H:i:s', '2015-01-01 00:00:00');
+        $expectedRows = [
+            array_fill(0, 10, $expectedDate),
+            array_fill(0, 10, $expectedDate),
+            array_fill(0, 10, $expectedDate),
+            array_merge(array_fill(0, 7, $expectedDate), ['', '', '']),
+        ];
+
+        $this->assertEquals($expectedRows, $allRows);
+    }
+
+    /**
+     * @return void
+     */
+    public function testReadShouldSupportDifferentDatesAsNumericTimestamp()
+    {
+        // make sure dates are always created with the same timezone
+        date_default_timezone_set('UTC');
+
+        $allRows = $this->getAllRowsForFile('sheet_with_different_numeric_value_dates.xlsx');
+
+        $expectedRows = [
+            [
+                \DateTime::createFromFormat('Y-m-d H:i:s', '2015-09-01 00:00:00'),
+                \DateTime::createFromFormat('Y-m-d H:i:s', '2015-09-02 00:00:00'),
+                \DateTime::createFromFormat('Y-m-d H:i:s', '2015-09-01 22:23:00'),
+            ],
+            [
+                \DateTime::createFromFormat('Y-m-d H:i:s', '1900-02-28 23:59:59'),
+                \DateTime::createFromFormat('Y-m-d H:i:s', '1900-03-01 00:00:00'),
+                \DateTime::createFromFormat('Y-m-d H:i:s', '1900-02-28 11:00:00'), // 1900-02-29 should be converted to 1900-02-28
+            ]
+        ];
+        $this->assertEquals($expectedRows, $allRows);
+    }
+
     /**
      * @return void
      */
diff --git a/tests/resources/xlsx/sheet_with_different_numeric_value_dates.xlsx b/tests/resources/xlsx/sheet_with_different_numeric_value_dates.xlsx
new file mode 100644
index 0000000..1f565c1
Binary files /dev/null and b/tests/resources/xlsx/sheet_with_different_numeric_value_dates.xlsx differ
diff --git a/tests/resources/xlsx/sheet_with_same_numeric_value_date_formatted_differently.xlsx b/tests/resources/xlsx/sheet_with_same_numeric_value_date_formatted_differently.xlsx
new file mode 100644
index 0000000..8f5a20c
Binary files /dev/null and b/tests/resources/xlsx/sheet_with_same_numeric_value_date_formatted_differently.xlsx differ