fix timezone problems in timesheet forms (#555)

src/Timesheet/UserDateTimeFactory.php

@@ -0,0 +1,82 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Timesheet;
+
+use App\Entity\User;
+use Symfony\Component\Security\Core\Authentication\Token\Storage\TokenStorageInterface;
+
+class UserDateTimeFactory
+{
+    /**
+     * @var \DateTimeZone
+     */
+    protected $timezone;
+
+    /**
+     * @param TokenStorageInterface $tokenStorage
+     */
+    public function __construct(TokenStorageInterface $tokenStorage)
+    {
+        if (null === $tokenStorage->getToken()) {
+            return;
+        }
+
+        /* @var $user User */
+        $user = $tokenStorage->getToken()->getUser();
+        $timezone = date_default_timezone_get();
+
+        if ($user instanceof User && null !== $user->getPreferenceValue('timezone')) {
+            $timezone = $user->getPreferenceValue('timezone');
+        }
+
+        $this->timezone = new \DateTimeZone($timezone);
+    }
+
+    /**
+     * @return \DateTimeZone
+     */
+    public function getTimezone()
+    {
+        return $this->timezone;
+    }
+
+    /**
+     * @return \DateTime
+     */
+    public function getStartOfMonth()
+    {
+        $date = $this->createDateTime('first day of this month');
+        $date->setTime(0, 0, 0);
+
+        return $date;
+    }
+
+    /**
+     * @return \DateTime
+     */
+    public function getEndOfMonth()
+    {
+        $date = $this->createDateTime('last day of this month');
+        $date->setTime(23, 59, 59);
+
+        return $date;
+    }
+
+    /**
+     * @param string $datetime
+     * @return \DateTime
+     */
+    public function createDateTime(string $datetime = 'now')
+    {
+        $date = new \DateTime($datetime, $this->timezone);
+
+        return $date;
+    }
+}