gistfile1.php

<?php

// DISPLAY YOUR AGE //

function whats_my_age_again($birthday) {
	extract( shortcode_atts( array(
		'birthday' => 'birthday'
	), $birthday));
	return date("Y", time() - strtotime($birthday)) - 1970;
}

add_shortcode('show-my-age', 'whats_my_age_again');