ce-use-12hr-clock.php

<?php
function community_events_12hr_time() {
	return 'g:i a';
}

function setup_time_option_filter() {
	add_action( 'pre_option_time_format', 'community_events_12hr_time' );
}

function teardown_time_option_filter() {
	remove_action( 'pre_option_time_format', 'community_events_12hr_time' );
}

add_action( 'tribe_events_community_section_before_datetime', 'setup_time_option_filter' );
add_action( 'tribe_events_community_section_after_datetime', 'teardown_time_option_filter' );