average ideal ferrary

t1.php

<?php

$date = new DateTime('0001-01-01');
$now = new DateTime('2022-01-01');
$count = 0;

while ($date < $now) {
    $isSuitable = false;

    if ((int)$date->format('m') === 2) {
        $d1 = clone $date;
        $d1->add(new DateInterval('P28D'));

        if ((int)$d1->format('m') > 2) {
            if ($date->format('D') === 'Mon') {
                $isSuitable = true;
            }
        }
    }

    if ($isSuitable) {
        echo ++$count . ': ' . $date->format('d-m-Y') . PHP_EOL;
    }

    $date->add(new DateInterval('P1M'));
}

echo 'Total: ' . $count . ' cases, average:  ' . (2021 / $count) . PHP_EOL;