Thanks for voting that as the solution!
With regards to your date/time issue, I personally used the 24 hour clock as it was easier, especially for sorting. To output it differently though, you can grab the time and then reformat it using the DateTime::createFromFormat function (http://php.net/manual/en/datetime.createfromformat.php)
// format Hi is 24 hour format hours and minutes, both with leading zero
// i.e. 1630, 0625, 1942 etc.
$event_time = DateTime::createFromFormat('Hi', get_field('event_time') );
//Output in 12 hour format without leading zeros and with am/pm.
// i.e. 12.30pm, 9.12am, 6.05pm
echo $event_time->format('g.ia');
