Shortcode to show the event countdown - basic version

EE Countdown Shortcode Basic

/*
Shortcode Name: Event Countdown
Author: Dean Robinson
Description: This code uses the espresso_countdown function in time_date.php to display a countdown to the event start date
Usage Example: [EVENT_COUNTDOWN]
Requirements: 
Notes: This needs to be added to the custom_shortcodes.php file that comes with the Custom Files Addon
*/
function ee_event_countdown() {

global $this_event_id;

$event_id = $this_event_id;

//Create the countdown variables
$start_timestamp = espresso_event_time($event_id, 'start_timestamp');
$end_timestamp = espresso_event_time($event_id, 'end_timestamp');

$countdown = espresso_countdown($start_timestamp, $end_timestamp, 'This event has ended' ); 
//Display the countup
return $countdown;

}
add_shortcode('EVENT_COUNTDOWN', 'ee_event_countdown');