public function testConstructorMitNegativerZeit()
 {
     $time = new MultiZeit("-10:00:00");
     $this->assertEquals("-10:00:00", $time->__toString());
     $this->assertEquals("-10:00:00", $time->format());
     $this->assertEquals("-10:00", $time->format("H:i"));
     $this->assertEquals(-10, $time->hour());
     $this->assertEquals(0, $time->minute());
     $this->assertEquals(0, $time->second());
     $this->assertEquals(-36000, $time->inSeconds());
 }
 public function subtract(MultiZeit $add)
 {
     return self::fromSeconds($this->inSeconds() - $add->inSeconds());
 }