diff --git a/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformer.php b/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformer.php
index ed90331266..280e4d4293 100644
--- a/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformer.php
+++ b/src/Symfony/Component/Form/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformer.php
@@ -81,7 +81,9 @@ class DateTimeToHtml5LocalDateTimeTransformer extends BaseDateTimeTransformer
             return;
         }
 
-        if (!preg_match('/^(\d{4})-(\d{2})-(\d{2})[T ]\d{2}:\d{2}(?::\d{2})?$/', $dateTimeLocal, $matches)) {
+        // to maintain backwards compatibility we do not strictly validate the submitted date
+        // see https://github.com/symfony/symfony/issues/28699
+        if (!preg_match('/^(\d{4})-(\d{2})-(\d{2})[T ]\d{2}:\d{2}(?::\d{2})?/', $dateTimeLocal, $matches)) {
             throw new TransformationFailedException(sprintf('The date "%s" is not a valid date.', $dateTimeLocal));
         }
 
diff --git a/src/Symfony/Component/Form/Tests/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformerTest.php b/src/Symfony/Component/Form/Tests/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformerTest.php
index 5dac998ad1..6046022e45 100644
--- a/src/Symfony/Component/Form/Tests/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformerTest.php
+++ b/src/Symfony/Component/Form/Tests/Extension/Core/DataTransformer/DateTimeToHtml5LocalDateTimeTransformerTest.php
@@ -51,6 +51,10 @@ class DateTimeToHtml5LocalDateTimeTransformerTest extends TestCase
             array('UTC', 'UTC', '2010-02-03 04:05:00 UTC', '2010-02-03T04:05'),
             array('America/New_York', 'Asia/Hong_Kong', '2010-02-03 04:05:00 America/New_York', '2010-02-03T17:05'),
             array('Europe/Amsterdam', 'Europe/Amsterdam', '2013-08-21 10:30:00 Europe/Amsterdam', '2013-08-21T10:30:00'),
+            array('UTC', 'UTC', '2018-09-15T10:00:00Z', '2018-09-15T10:00:00Z'),
+            array('Europe/Berlin', 'Europe/Berlin', '2018-09-15T10:00:00+02:00', '2018-09-15T10:00:00+02:00'),
+            array('Europe/Berlin', 'Europe/Berlin', '2018-09-15T10:00:00+0200', '2018-09-15T10:00:00+0200'),
+            array('UTC', 'UTC', '2018-10-03T10:00:00.000Z', '2018-10-03T10:00:00.000Z'),
         );
     }