Problems with eo_format_datetime_range

Hello!

I’m trying to figure out how to output the dates in my custom event list template with eo_format_datetime_range like shown on http://plugin226.rssing.com/chan-12548603/all_p150.html.

If I echo $date1 or $date2 in the template, the dates are shown and are correct, but the use of echo eo_format_datetime_range( $date1, $date2, $format, $seperator = ‘ – ‘, $is_rtl = null ); always fails.

Here is my template:

<?php
/**
 * Add this to your theme for it to take affect.
 */

global $eo_event_loop,$eo_event_loop_args;

//Date % Time format for events
$date_format = get_option('date_format');
$time_format = get_option('time_format');

//The list ID / classes
$id = ( $eo_event_loop_args['id'] ? 'id="'.$eo_event_loop_args['id'].'"' : '' );
$classes = $eo_event_loop_args['class'];

$current_month = false;

?>

<?php if( $eo_event_loop->have_posts() ): ?>

        <?php while( $eo_event_loop->have_posts() ): $eo_event_loop->the_post(); ?>

            <?php 
            if( $current_month != eo_get_the_start('m') ){

                    //End previous group
                    echo '</ul>';
                    //Start new group
                    echo '<h3>'.eo_get_the_start('F Y').'</h3>';
                    echo '<ul>';
            }
            $current_month = eo_get_the_start('m');

            //Generate HTML classes for this event
            $eo_event_classes = eo_get_event_classes(); 

            //For non-all-day events, include time format
            ///$format = ( eo_is_all_day() ? $date_format : $date_format. '--' .$time_format );

            ?>

            <li class="<?php echo esc_attr(implode(' ',$eo_event_classes)); ?>" >
                <a href="<?php the_permalink();?>" title="<?php the_title_attribute(); ?>" >
                     <?php the_title(); ?>
                </a> 
<?php
$date1 = eo_get_the_start('jS F Y');
$date2 = eo_get_the_end('jS F Y');
$format = 'jS F Y'; //Format date as "1st June 2015";

//3.0.0+ only:
echo eo_format_datetime_range( $date1, $date2, $format, $seperator = ' &ndash; ', $is_rtl = null );
?>
                <?php echo __('<br>','eventorganiser') . ' '.eo_get_the_start($format). ' to ' .eo_get_the_end($time_format); ?>
            </li>

        <?php endwhile; ?>

<?php elseif( ! empty($eo_event_loop_args['no_events']) ): ?>

    <ul id="<?php echo esc_attr($id);?>" class="<?php echo esc_attr($classes);?>" > 
        <li class="eo-no-events" > <?php echo $eo_event_loop_args['no_events']; ?> </li>
    </ul>

<?php endif; ?>

Hopefully somebody can help me with this as I am no programmer.

Thanks a lot!
Christian