diff --git a/src/PhpSpreadsheet/Calculation/DateTimeExcel/DateParts.php b/src/PhpSpreadsheet/Calculation/DateTimeExcel/DateParts.php
index b669eb0a1e..7bb03c9da8 100644
--- a/src/PhpSpreadsheet/Calculation/DateTimeExcel/DateParts.php
+++ b/src/PhpSpreadsheet/Calculation/DateTimeExcel/DateParts.php
@@ -47,6 +47,7 @@ public static function day($dateValue)
 
         // Execute function
         $PHPDateObject = SharedDateHelper::excelToDateTimeObject($dateValue);
+        SharedDateHelper::roundMicroseconds($PHPDateObject);
 
         return (int) $PHPDateObject->format('j');
     }
@@ -85,6 +86,7 @@ public static function month($dateValue)
 
         // Execute function
         $PHPDateObject = SharedDateHelper::excelToDateTimeObject($dateValue);
+        SharedDateHelper::roundMicroseconds($PHPDateObject);
 
         return (int) $PHPDateObject->format('n');
     }
@@ -123,6 +125,7 @@ public static function year($dateValue)
         }
         // Execute function
         $PHPDateObject = SharedDateHelper::excelToDateTimeObject($dateValue);
+        SharedDateHelper::roundMicroseconds($PHPDateObject);
 
         return (int) $PHPDateObject->format('Y');
     }
diff --git a/src/PhpSpreadsheet/Calculation/DateTimeExcel/TimeParts.php b/src/PhpSpreadsheet/Calculation/DateTimeExcel/TimeParts.php
index d9b99f3c36..e1331b0109 100644
--- a/src/PhpSpreadsheet/Calculation/DateTimeExcel/TimeParts.php
+++ b/src/PhpSpreadsheet/Calculation/DateTimeExcel/TimeParts.php
@@ -46,6 +46,7 @@ public static function hour($timeValue)
         // Execute function
         $timeValue = fmod($timeValue, 1);
         $timeValue = SharedDateHelper::excelToDateTimeObject($timeValue);
+        SharedDateHelper::roundMicroseconds($timeValue);
 
         return (int) $timeValue->format('H');
     }
@@ -86,6 +87,7 @@ public static function minute($timeValue)
         // Execute function
         $timeValue = fmod($timeValue, 1);
         $timeValue = SharedDateHelper::excelToDateTimeObject($timeValue);
+        SharedDateHelper::roundMicroseconds($timeValue);
 
         return (int) $timeValue->format('i');
     }
@@ -126,6 +128,7 @@ public static function second($timeValue)
         // Execute function
         $timeValue = fmod($timeValue, 1);
         $timeValue = SharedDateHelper::excelToDateTimeObject($timeValue);
+        SharedDateHelper::roundMicroseconds($timeValue);
 
         return (int) $timeValue->format('s');
     }
diff --git a/src/PhpSpreadsheet/Shared/Date.php b/src/PhpSpreadsheet/Shared/Date.php
index 4f19673113..9f5abe34d9 100644
--- a/src/PhpSpreadsheet/Shared/Date.php
+++ b/src/PhpSpreadsheet/Shared/Date.php
@@ -223,11 +223,13 @@ public static function excelToDateTimeObject($excelTimestamp, $timeZone = null)
 
         $days = floor($excelTimestamp);
         $partDay = $excelTimestamp - $days;
-        $hours = floor($partDay * 24);
-        $partDay = $partDay * 24 - $hours;
-        $minutes = floor($partDay * 60);
-        $partDay = $partDay * 60 - $minutes;
-        $seconds = round($partDay * 60);
+        $hms = 86400 * $partDay;
+        $microseconds = (int) round(fmod($hms, 1) * 1000000);
+        $hms = (int) floor($hms);
+        $hours = intdiv($hms, 3600);
+        $hms -= $hours * 3600;
+        $minutes = intdiv($hms, 60);
+        $seconds = $hms % 60;
 
         if ($days >= 0) {
             $days = '+' . $days;
@@ -235,7 +237,7 @@ public static function excelToDateTimeObject($excelTimestamp, $timeZone = null)
         $interval = $days . ' days';
 
         return $baseDate->modify($interval)
-            ->setTime((int) $hours, (int) $minutes, (int) $seconds);
+            ->setTime((int) $hours, (int) $minutes, (int) $seconds, (int) $microseconds);
     }
 
     /**
@@ -252,8 +254,10 @@ public static function excelToDateTimeObject($excelTimestamp, $timeZone = null)
      */
     public static function excelToTimestamp($excelTimestamp, $timeZone = null)
     {
-        return (int) self::excelToDateTimeObject($excelTimestamp, $timeZone)
-            ->format('U');
+        $dto = self::excelToDateTimeObject($excelTimestamp, $timeZone);
+        self::roundMicroseconds($dto);
+
+        return (int) $dto->format('U');
     }
 
     /**
@@ -287,13 +291,15 @@ public static function PHPToExcel($dateValue)
      */
     public static function dateTimeToExcel(DateTimeInterface $dateValue)
     {
+        $seconds = (float) sprintf('%d.%06d', $dateValue->format('s'), $dateValue->format('u'));
+
         return self::formattedPHPToExcel(
             (int) $dateValue->format('Y'),
             (int) $dateValue->format('m'),
             (int) $dateValue->format('d'),
             (int) $dateValue->format('H'),
             (int) $dateValue->format('i'),
-            (int) $dateValue->format('s')
+            $seconds
         );
     }
 
@@ -323,7 +329,7 @@ public static function timestampToExcel($unixTimestamp)
      * @param int $day
      * @param int $hours
      * @param int $minutes
-     * @param int $seconds
+     * @param float|int $seconds
      *
      * @return float Excel date/time value
      */
@@ -553,4 +559,12 @@ public static function formattedDateTimeFromTimestamp(string $date, string $form
 
         return $dtobj->format($format);
     }
+
+    public static function roundMicroseconds(DateTime $dti): void
+    {
+        $microseconds = (int) $dti->format('u');
+        if ($microseconds >= 500000) {
+            $dti->modify('+1 second');
+        }
+    }
 }
diff --git a/src/PhpSpreadsheet/Style/NumberFormat/DateFormatter.php b/src/PhpSpreadsheet/Style/NumberFormat/DateFormatter.php
index ba54b53593..d1826ea77b 100644
--- a/src/PhpSpreadsheet/Style/NumberFormat/DateFormatter.php
+++ b/src/PhpSpreadsheet/Style/NumberFormat/DateFormatter.php
@@ -166,6 +166,37 @@ public static function format($value, string $format): string
         // Excel 2003 XML formats, m will not have been changed to i above.
         // Change it now.
         $format = (string) \preg_replace('/\\\\:m/', ':i', $format);
+        $microseconds = (int) $dateObj->format('u');
+        if (strpos($format, ':s.000') !== false) {
+            $milliseconds = (int) round($microseconds / 1000.0);
+            if ($milliseconds === 1000) {
+                $milliseconds = 0;
+                $dateObj->modify('+1 second');
+            }
+            $dateObj->modify("-$microseconds microseconds");
+            $format = str_replace(':s.000', ':s.' . sprintf('%03d', $milliseconds), $format);
+        } elseif (strpos($format, ':s.00') !== false) {
+            $centiseconds = (int) round($microseconds / 10000.0);
+            if ($centiseconds === 100) {
+                $centiseconds = 0;
+                $dateObj->modify('+1 second');
+            }
+            $dateObj->modify("-$microseconds microseconds");
+            $format = str_replace(':s.00', ':s.' . sprintf('%02d', $centiseconds), $format);
+        } elseif (strpos($format, ':s.0') !== false) {
+            $deciseconds = (int) round($microseconds / 100000.0);
+            if ($deciseconds === 10) {
+                $deciseconds = 0;
+                $dateObj->modify('+1 second');
+            }
+            $dateObj->modify("-$microseconds microseconds");
+            $format = str_replace(':s.0', ':s.' . sprintf('%1d', $deciseconds), $format);
+        } else { // no fractional second
+            if ($microseconds >= 500000) {
+                $dateObj->modify('+1 second');
+            }
+            $dateObj->modify("-$microseconds microseconds");
+        }
 
         return $dateObj->format($format);
     }
diff --git a/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php b/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php
index 23af522269..4f13264ffd 100644
--- a/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php
+++ b/tests/PhpSpreadsheetTests/Reader/Xlsx/ExplicitDateTest.php
@@ -35,7 +35,7 @@ public static function testExplicitDate(): void
         $value = $sheet->getCell('A3')->getValue();
         $formatted = $sheet->getCell('A3')->getFormattedValue();
         self::assertEqualsWithDelta(44561.98948, $value, 0.00001);
-        self::assertSame('2021-12-31 23:44:51', $formatted);
+        self::assertSame('2021-12-31 23:44:52', $formatted);
         // Date only
         $value = $sheet->getCell('B3')->getValue();
         $formatted = $sheet->getCell('B3')->getFormattedValue();
@@ -45,7 +45,7 @@ public static function testExplicitDate(): void
         $value = $sheet->getCell('C3')->getValue();
         $formatted = $sheet->getCell('C3')->getFormattedValue();
         self::assertEqualsWithDelta(0.98948, $value, 0.00001);
-        self::assertSame('23:44:51', $formatted);
+        self::assertSame('23:44:52', $formatted);
 
         $spreadsheet->disconnectWorksheets();
     }
diff --git a/tests/data/Style/NumberFormatDates.php b/tests/data/Style/NumberFormatDates.php
index 42fbc4ea09..632b967e03 100644
--- a/tests/data/Style/NumberFormatDates.php
+++ b/tests/data/Style/NumberFormatDates.php
@@ -43,10 +43,25 @@
         'yyyy/mm/dd\ h:mm:ss.000',
     ],
     [
-        '2023/02/28 07:35:02.000',
+        '2023/02/28 07:35:02.400',
         44985.316,
         'yyyy/mm/dd\ hh:mm:ss.000',
     ],
+    [
+        '2023/02/28 07:35:13.067',
+        44985.316123456,
+        'yyyy/mm/dd\ hh:mm:ss.000',
+    ],
+    [
+        '2023/02/28 07:35:13.07',
+        44985.316123456,
+        'yyyy/mm/dd\ hh:mm:ss.00',
+    ],
+    [
+        '2023/02/28 07:35:13.1',
+        44985.316123456,
+        'yyyy/mm/dd\ hh:mm:ss.0',
+    ],
     [
         '07:35:00 AM',
         43270.315972222,