Example.

example.php

<?php //Please do not include the opening PHP tag if you already have one 

function ee_events_shortcode( $atts ) {
    
    //Pull the sites date and time formats.
    $date_format        = get_option( 'date_format' );
    $time_format        = get_option( 'time_format' );

    //Pull upcoming events
    $events = EEM_Event::instance()->get_upcoming_events(array(
                        'limit'    => 1,
                        'order_by' => array('Datetime.DTT_EVT_start' => 'ASC')
                    ));
    
     // content-header
    echo "BEGIN:VCALENDAR" . "<br>";
    echo "VERSION:2.0" . "<br>";
    echo "PRODID:-//" . the_title() . "//NONSGML Events //EN" . "<br>";
    echo "X-WR-CALNAME:" . the_title() . _e(' - Events','themeforce') . "<br>";
    echo "X-ORIGINAL-URL:" . the_permalink() . "<br>";
    echo "X-WR-CALDESC:" , the_title() . _e(' - Events','themeforce') . "<br>";
    echo "CALSCALE:GREGORIAN" . "<br>";
    
    foreach( $events as $event ) {
        
        echo "BEGIN:VEVENT" . "<br>";
          
        // Pull the next upcoming datetime for this event.
        $datetimes = EEM_Datetime::instance()->get_datetimes_for_event_ordered_by_start_time( $event->ID(), $show_expired = false, $show_archived = false, $limit = null );
        // Reset the datetimes pointer to the earliest datetime and use that one.
        $datetime = reset( $datetimes );
            if ($datetime instanceof EE_Datetime) {
                echo 'ID:' . $event->ID() . '<br>';
                echo 'Title:' . $event->name() . '<br>';
                echo 'Start Date:' . date_i18n( $date_format, strtotime( $datetime->start_date('Y-m-d') ) ) . '<br>';
                echo 'End Date:' . date_i18n( $date_format, strtotime( $datetime->start_date('Y-m-d') ) ) . '<br>';
                // Loop over each datetime we have pulled from the database and output
                foreach ($datetimes as $datetime) {
                    echo 'Datetime ID:' . $datetime->ID() . '<br>';
                    echo 'Date:' . date_i18n( $date_format . ' ' . $time_format, strtotime( $datetime->start_date_and_time('Y-m-d', 'H:i:s') ) ) . '<br>';
                    echo 'Date:' . date_i18n( $date_format, strtotime( $datetime->start_date('Y-m-d') ) ) . '<br>';
                    echo 'Start Date:' . date_i18n( $time_format, strtotime( $datetime->start_time('H:i:s') ) ) . '<br>';
                    echo 'End Date:' .  date_i18n( $time_format, strtotime( $datetime->end_time('H:i:s') ) ) . '<br>';
                //end foreach $datetimes
                };
            };
        
        //$geteventdate = $event->first_datetime(); 
        //$eventdate = date('Y-m-d H:i:s', strtotime($geteventdate->start_date()));
        //echo "DTSTART:" . $eventdate . "<br>"; 
        //echo "DTSTART:";
        //do_shortcode( '[TIME_START]' );
        //echo "<br>";
        //do_shortcode( '[ESPRESSO_EVENTS_TABLE_TEMPLATE show_all_datetimes=TRUE]' );
        //echo "<br>";
      
        
        //echo "DTEND:" . "" . "<br>";
        //echo "DTEND:" . $event->get('DTT_EVT_end'). "<br>";
        echo "SUMMARY:" . $event->name() . "<br>";
        echo "DESCRIPTION:" . $event->name() . "<br>";
        //echo "DESCRIPTION:" . $event->description() . "<br>";
        echo "END:VEVENT" . "<br>";
        $startdate = "";
    }
echo "END:VCALENDAR" . "<br>";
}
add_shortcode( 'ee_events_shortcode_output', 'ee_events_shortcode');