<?php
    $start_time = get_field('start_time');

    $end_time = get_field('end_time');

    if ( !empty($start_time) ) { echo '<div class="entry-meta start-time"><span>' . $start_time . '&nbsp;</span></div>' ;}

    if ( !empty($end_time) ) { echo '<div class="entry-meta end-time"><span>-&nbsp;' . $end_time . '</span></div>' ;}
?>