Add to iCal in Event Espresso adds the wrong time to iCal. Could be due to your timezone setting. By default WordPress is set to UTC, ‘Universal Time’. In my opinion you should leave it at this and any scripts or plugins you write can be amended with the local timestamp which you can use like:
$local_timestamp = get_the_time('U');
But to solve the original issue with Event Espresso iCal error if you timezone was left to default, you need to change the end of the timestamp in the iCal form. In, “(plugins) EE/modules/ical/EED_Ical.module.php” you can change the line on line 27 from;
const iCal_datetime_format = 'Ymd\THis\Z';
to
const iCal_datetime_format = 'Ymd\THis';