Calculate in php date 6 yeats and 30 days ago

I am beginner in php.

I have this code in php 8.1:

$date = date('Y-m-d', strtotime('-30 days'));
echo $date;

It’s work fine, but i need date 6 years and 30 days ago. How can i check it?
I need date calculate from now

Please help me.