convert timesheets to UTC with support for user timezone (#372)

tests/Invoice/Calculator/AbstractInvoiceCalculatorTest.php

@@ -68,6 +68,7 @@ abstract class AbstractCalculatorTest extends TestCase
         $timesheet = new Timesheet();
         $timesheet
             ->setDescription('timesheet description')
+            ->setBegin(new \DateTime())
             ->setDuration(3600)
             ->setRate(293.27)
             ->setUser(new User())

tests/Invoice/Renderer/DebugRenderer.php

@@ -44,6 +44,15 @@ class DebugRenderer implements RendererInterface
         return $date->format('d.m.Y');
     }
 
+    /**
+     * @param \DateTime $date
+     * @return mixed
+     */
+    protected function getFormattedTime(\DateTime $date)
+    {
+        return $date->format('H:i');
+    }
+
     /**
      * @param $amount
      * @return mixed