Hi @rootshift,
Just working through this with @elliot so close to a solution.
Once this has been worked out, I’ll post up the solution.
But basically, you should be able to do this for your button:
<?php
$event_end_date = DateTime::createFromFormat('Ymd', get_field('your_event_end_field'));
if ( $event_end_date->format('Ymd') < date('Ymd') ) { ?>
<a href="#">Volunteer link</a>
<?php } else { ?>
Volunteering no longer available
<?php } ?>
