public function testPreviousYear()
 {
     $objDate = new class_date(20130122120000);
     $objDate->setPreviousYear();
     $this->assertEquals($objDate->getLongTimestamp(), 20120122120000);
     $objDate = new class_date(20150531120000);
     $objDate->setPreviousYear();
     $this->assertEquals($objDate->getLongTimestamp(), 20140531120000);
 }