Revert "use timezone of event"

This reverts commit 9662e1f333.

tests/LocalDateTimeTest.php

@@ -0,0 +1,12 @@
+<?php
+declare(strict_types=1);
+
+use MobilizonConnector\LocalDateTime;
+use PHPUnit\Framework\TestCase;
+
+final class LocalDateTimeTest extends TestCase {
+  public function testCanGet24TimeForUsualTime(): void {
+    $d = new LocalDateTime('2020-12-24T16:45:00Z', new DateTimeZone("utc"));
+    $this->assertEquals(new DateTimeImmutable('2020-12-24T16:45:00Z'), $d->getValue());
+  }
+}