diff --git a/src/PhpSpreadsheet/Document/Properties.php b/src/PhpSpreadsheet/Document/Properties.php
index 3be5a67a..2d461c59 100644
--- a/src/PhpSpreadsheet/Document/Properties.php
+++ b/src/PhpSpreadsheet/Document/Properties.php
@@ -115,7 +115,7 @@ class Properties
         // Initialise values
         $this->lastModifiedBy = $this->creator;
         $this->created = self::intOrFloatTimestamp(null);
-        $this->modified = self::intOrFloatTimestamp(null);
+        $this->modified = $this->created;
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Document/PropertiesTest.php b/tests/PhpSpreadsheetTests/Document/PropertiesTest.php
index e6c95cd4..0dfb256b 100644
--- a/tests/PhpSpreadsheetTests/Document/PropertiesTest.php
+++ b/tests/PhpSpreadsheetTests/Document/PropertiesTest.php
@@ -2,6 +2,7 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Document;
 
+use DateTime;
 use DateTimeZone;
 use PhpOffice\PhpSpreadsheet\Document\Properties;
 use PhpOffice\PhpSpreadsheet\Shared\Date;
@@ -14,20 +15,27 @@ class PropertiesTest extends TestCase
      */
     private $properties;
 
+    /** @var float */
+    private $startTime;
+
     protected function setup(): void
     {
-        $this->properties = new Properties();
+        do {
+            // loop to avoid rare situation where timestamp changes
+            $this->startTime = (float) (new DateTime())->format('U');
+            $this->properties = new Properties();
+            $endTime = (float) (new DateTime())->format('U');
+        } while ($this->startTime !== $endTime);
     }
 
     public function testNewInstance(): void
     {
-        $createdTime = $modifiedTime = time();
         self::assertSame('Unknown Creator', $this->properties->getCreator());
         self::assertSame('Unknown Creator', $this->properties->getLastModifiedBy());
         self::assertSame('Untitled Spreadsheet', $this->properties->getTitle());
         self::assertSame('', $this->properties->getCompany());
-        self::assertSame($createdTime, $this->properties->getCreated());
-        self::assertSame($modifiedTime, $this->properties->getModified());
+        self::assertEquals($this->startTime, $this->properties->getCreated());
+        self::assertEquals($this->startTime, $this->properties->getModified());
     }
 
     public function testSetCreator(): void
@@ -46,10 +54,10 @@ class PropertiesTest extends TestCase
      */
     public function testSetCreated($expectedCreationTime, $created): void
     {
-        $expectedCreationTime = $expectedCreationTime ?? time();
+        $expectedCreationTime = $expectedCreationTime ?? $this->startTime;
 
         $this->properties->setCreated($created);
-        self::assertSame($expectedCreationTime, $this->properties->getCreated());
+        self::assertEquals($expectedCreationTime, $this->properties->getCreated());
     }
 
     public function providerCreationTime(): array
@@ -78,10 +86,10 @@ class PropertiesTest extends TestCase
      */
     public function testSetModified($expectedModifiedTime, $modified): void
     {
-        $expectedModifiedTime = $expectedModifiedTime ?? time();
+        $expectedModifiedTime = $expectedModifiedTime ?? $this->startTime;
 
         $this->properties->setModified($modified);
-        self::assertSame($expectedModifiedTime, $this->properties->getModified());
+        self::assertEquals($expectedModifiedTime, $this->properties->getModified());
     }
 
     public function providerModifiedTime(): array