Solved! Thanks to James and a help ticket and this blog post: http://joshuaiz.com/words/ordering-events-by-advanced-custom-fields-date-time-picker-field/
First I changed the date&time field output to a unix timestamp, to do so just put a capital U under custom.
then add:
$eventTIME = get_sub_field('event_date_time');
$today = current_time('timestamp'); // Get current unix timestamp
if($eventTIME<$today) continue;
If the event date is smaller than today’s date it skips it.
However, all my pretty dates were now displaying as unix timestamps. I changed the code to display them to this:
<?php $start = get_sub_field('event_date_time'); echo date_i18n('F j, Y - g:i a', $start); ?>
And done!
