- date_format: documentation ( source)
<?php
$today = new DateTime();
$last_year=(new DateTime())->sub(new DateInterval('P1Y'));
$next_year = (new DateTime())->add(new DateInterval('P1Y'));
echo date_format($last_year, 'Y').' '.date_format($today, 'Y').' '.date_format($next_year, 'Y');