Fixes timezone issues on editing events

This commit changes the implementation of the DateTransformer in such a
way that dates are now handled using a provided dateTime. When no
dateTime is provided UTC is used.

Not using this handler caused dates to change when editing an event.

app/src/Event/EventFormType.php

@@ -55,7 +55,15 @@ public function getName()
      */
     public function buildForm(FormBuilderInterface $builder, array $options)
     {
+
         list ($continents, $cities) = $this->getListOfTimezoneContinentsAndCities();
+
+        $timezone = null;
+        if (isset($options['data'])) {
+            $timezone = $options['data']->getFullTimezone();
+        }
+
+        $dateTransformer = new DateTransformer($timezone);
         $builder
             ->add('addr', 'hidden', ['mapped' => false])
             ->add(
@@ -107,29 +115,29 @@ public function buildForm(FormBuilderInterface $builder, array $options)
                     'start_date',
                     'text',
                     $this->getOptionsForDateWidget('Start date')
-                )->addViewTransformer(new DateTransformer())
+                )->addViewTransformer($dateTransformer)
             )
             ->add(
                 $builder->create(
                     'end_date',
                     'text',
                     $this->getOptionsForDateWidget('End date')
-                )->addViewTransformer(new DateTransformer())
+                )->addViewTransformer($dateTransformer)
             )
             ->add('href', 'url', $this->getOptionsForUrlWidget('Website URL'))
             ->add(
                 $builder->create(
                     'cfp_start_date',
                     'text',
                     $this->getOptionsForDateWidget('Opening date', false)
-                )->addViewTransformer(new DateTransformer())
+                )->addViewTransformer($dateTransformer)
             )
             ->add(
                 $builder->create(
                     'cfp_end_date',
                     'text',
                     $this->getOptionsForDateWidget('Closing date', false)
-                )->addViewTransformer(new DateTransformer())
+                )->addViewTransformer($dateTransformer)
             )
             ->add('cfp_url', 'url', $this->getOptionsForUrlWidget('Call for papers URL', false))
             ->add(

app/src/Form/DataTransformer/DateTransformer.php

@@ -2,9 +2,21 @@
 namespace Form\DataTransformer;
 
 use Symfony\Component\Form\DataTransformerInterface;
+use \DateTime;
+use \DateTimeZone;
 
 class DateTransformer implements DataTransformerInterface
 {
+    protected $timezone;
+
+    public function __construct($timezone = 'UTC')
+    {
+        if (! in_array($timezone, DateTimeZone::listIdentifiers(DateTimeZone::ALL))) {
+            $timezone = 'UTC';
+        }
+        $this->timezone = new DateTimeZone($timezone);
+    }
+
     public function transform($value)
     {
         return $this->convertDate($value, 'j F Y');
@@ -18,9 +30,9 @@ public function reverseTransform($value)
     protected function convertDate($value, $format)
     {
         if ($value) {
-            $d = strtotime($value);
+            $d = new DateTime($value, $this->timezone);
             if ($d) {
-                $value = date($format, $d);
+                $value = $d->format($format);
             }
         }
         return $value;