diff --git a/src/Symfony/Component/Form/Extension/Core/Type/DateType.php b/src/Symfony/Component/Form/Extension/Core/Type/DateType.php
index 0b9a4ffab3..88f5457625 100644
--- a/src/Symfony/Component/Form/Extension/Core/Type/DateType.php
+++ b/src/Symfony/Component/Form/Extension/Core/Type/DateType.php
@@ -381,9 +381,7 @@ class DateType extends AbstractType
         $result = [];
 
         foreach ($years as $year) {
-            if (false !== $y = gmmktime(0, 0, 0, 6, 15, $year)) {
-                $result[$y] = $year;
-            }
+            $result[\PHP_INT_SIZE === 4 ? \DateTime::createFromFormat('Y e', $year.' UTC')->format('U') : gmmktime(0, 0, 0, 6, 15, $year)] = $year;
         }
 
         return $result;
diff --git a/src/Symfony/Component/Form/Tests/Extension/Core/Type/DateTypeTest.php b/src/Symfony/Component/Form/Tests/Extension/Core/Type/DateTypeTest.php
index 5891cc08aa..a4f93cdee2 100644
--- a/src/Symfony/Component/Form/Tests/Extension/Core/Type/DateTypeTest.php
+++ b/src/Symfony/Component/Form/Tests/Extension/Core/Type/DateTypeTest.php
@@ -927,19 +927,15 @@ class DateTypeTest extends BaseTypeTest
         $this->assertSame([$error], iterator_to_array($form->getErrors()));
     }
 
-    public function testYearsFor32BitsMachines()
+    public function testYears()
     {
-        if (4 !== \PHP_INT_SIZE) {
-            $this->markTestSkipped('PHP 32 bit is required.');
-        }
-
         $view = $this->factory->create(static::TESTED_TYPE, null, [
-            'years' => range(1900, 2040),
+            'years' => [1900, 2000, 2040],
         ])
             ->createView();
 
         $listChoices = [];
-        foreach (range(1902, 2037) as $y) {
+        foreach ([1900, 2000, 2040] as $y) {
             $listChoices[] = new ChoiceView($y, $y, $y);
         }
 
diff --git a/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php b/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php
index 317510c236..5011ee3321 100644
--- a/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php
+++ b/src/Symfony/Component/Intl/DateFormatter/IntlDateFormatter.php
@@ -180,7 +180,7 @@ abstract class IntlDateFormatter
     /**
      * Format the date/time value (timestamp) as a string.
      *
-     * @param int|\DateTimeInterface $timestamp The timestamp to format
+     * @param int|string|\DateTimeInterface $timestamp The timestamp to format
      *
      * @return string|bool The formatted value or false if formatting failed
      *
@@ -192,11 +192,15 @@ abstract class IntlDateFormatter
     {
         // intl allows timestamps to be passed as arrays - we don't
         if (\is_array($timestamp)) {
-            $message = 'Only integer Unix timestamps and DateTime objects are supported';
+            $message = 'Only Unix timestamps and DateTime objects are supported';
 
             throw new MethodArgumentValueNotImplementedException(__METHOD__, 'timestamp', $timestamp, $message);
         }
 
+        if (\is_string($timestamp) && $dt = \DateTime::createFromFormat('U', $timestamp)) {
+            $timestamp = $dt;
+        }
+
         // behave like the intl extension
         $argumentError = null;
         if (!\is_int($timestamp) && !$timestamp instanceof \DateTimeInterface) {
@@ -212,7 +216,7 @@ abstract class IntlDateFormatter
         }
 
         if ($timestamp instanceof \DateTimeInterface) {
-            $timestamp = $timestamp->getTimestamp();
+            $timestamp = $timestamp->format('U');
         }
 
         $transformer = new FullTransformer($this->getPattern(), $this->getTimeZoneId());
@@ -586,8 +590,7 @@ abstract class IntlDateFormatter
      */
     protected function createDateTime($timestamp)
     {
-        $dateTime = new \DateTime();
-        $dateTime->setTimestamp($timestamp);
+        $dateTime = \DateTime::createFromFormat('U', $timestamp);
         $dateTime->setTimezone($this->dateTimeZone);
 
         return $dateTime;
diff --git a/src/Symfony/Component/Intl/Tests/DateFormatter/IntlDateFormatterTest.php b/src/Symfony/Component/Intl/Tests/DateFormatter/IntlDateFormatterTest.php
index de61e7fb84..fd562b4d48 100644
--- a/src/Symfony/Component/Intl/Tests/DateFormatter/IntlDateFormatterTest.php
+++ b/src/Symfony/Component/Intl/Tests/DateFormatter/IntlDateFormatterTest.php
@@ -72,7 +72,7 @@ class IntlDateFormatterTest extends AbstractIntlDateFormatterTest
         } catch (\Exception $e) {
             $this->assertInstanceOf(MethodArgumentValueNotImplementedException::class, $e);
 
-            $this->assertStringEndsWith('Only integer Unix timestamps and DateTime objects are supported.  Please install the "intl" extension for full localization capabilities.', $e->getMessage());
+            $this->assertStringEndsWith('Only Unix timestamps and DateTime objects are supported.  Please install the "intl" extension for full localization capabilities.', $e->getMessage());
         }
     }
 
diff --git a/src/Symfony/Component/Yaml/Inline.php b/src/Symfony/Component/Yaml/Inline.php
index 935a7b5fc1..a317bb0438 100644
--- a/src/Symfony/Component/Yaml/Inline.php
+++ b/src/Symfony/Component/Yaml/Inline.php
@@ -674,17 +674,22 @@ class Inline
                     case Parser::preg_match('/^(-|\+)?[0-9][0-9_]*(\.[0-9_]+)?$/', $scalar):
                         return (float) str_replace('_', '', $scalar);
                     case Parser::preg_match(self::getTimestampRegex(), $scalar):
+                        // When no timezone is provided in the parsed date, YAML spec says we must assume UTC.
+                        $time = new \DateTime($scalar, new \DateTimeZone('UTC'));
+
                         if (Yaml::PARSE_DATETIME & $flags) {
-                            // When no timezone is provided in the parsed date, YAML spec says we must assume UTC.
-                            return new \DateTime($scalar, new \DateTimeZone('UTC'));
+                            return $time;
                         }
 
-                        $timeZone = date_default_timezone_get();
-                        date_default_timezone_set('UTC');
-                        $time = strtotime($scalar);
-                        date_default_timezone_set($timeZone);
+                        try {
+                            if (false !== $scalar = $time->getTimestamp()) {
+                                return $scalar;
+                            }
+                        } catch (\ValueError $e) {
+                            // no-op
+                        }
 
-                        return $time;
+                        return $time->format('U');
                 }
         }
 
diff --git a/src/Symfony/Component/Yaml/Tests/InlineTest.php b/src/Symfony/Component/Yaml/Tests/InlineTest.php
index ec0e182174..b1f0206d54 100644
--- a/src/Symfony/Component/Yaml/Tests/InlineTest.php
+++ b/src/Symfony/Component/Yaml/Tests/InlineTest.php
@@ -323,7 +323,7 @@ class InlineTest extends TestCase
             ['2007-10-30T02:59:43Z', gmmktime(2, 59, 43, 10, 30, 2007)],
             ['2007-10-30 02:59:43 Z', gmmktime(2, 59, 43, 10, 30, 2007)],
             ['1960-10-30 02:59:43 Z', gmmktime(2, 59, 43, 10, 30, 1960)],
-            ['1730-10-30T02:59:43Z', gmmktime(2, 59, 43, 10, 30, 1730)],
+            ['1730-10-30T02:59:43Z', \PHP_INT_SIZE === 4 ? '-7547547617' : gmmktime(2, 59, 43, 10, 30, 1730)],
 
             ['"a \\"string\\" with \'quoted strings inside\'"', 'a "string" with \'quoted strings inside\''],
             ["'a \"string\" with ''quoted strings inside'''", 'a "string" with \'quoted strings inside\''],
@@ -394,7 +394,7 @@ class InlineTest extends TestCase
             ['2007-10-30T02:59:43Z', gmmktime(2, 59, 43, 10, 30, 2007)],
             ['2007-10-30 02:59:43 Z', gmmktime(2, 59, 43, 10, 30, 2007)],
             ['1960-10-30 02:59:43 Z', gmmktime(2, 59, 43, 10, 30, 1960)],
-            ['1730-10-30T02:59:43Z', gmmktime(2, 59, 43, 10, 30, 1730)],
+            ['1730-10-30T02:59:43Z', \PHP_INT_SIZE === 4 ? '-7547547617' : gmmktime(2, 59, 43, 10, 30, 1730)],
 
             ['"a \\"string\\" with \'quoted strings inside\'"', 'a "string" with \'quoted strings inside\''],
             ["'a \"string\" with ''quoted strings inside'''", 'a "string" with \'quoted strings inside\''],