The version I posted above is actually used by the calendar grid display. Here is an rsvpmaker_upcoming query
SELECT SQL_CALC_FOUND_ROWS DISTINCT wpb_posts.*, meta_value as datetime, meta_id FROM wpb_posts JOIN wpb_postmeta ON wpb_postmeta.post_id = wpb_posts.ID AND meta_key=’_rsvp_dates’ WHERE 1=1 AND wpb_posts.post_type = ‘rsvpmaker’ AND ((wpb_posts.post_status = ‘publish’)) AND meta_key=’_rsvp_dates’ AND meta_value > CURDATE( ) AND meta_value < DATE_ADD(CURDATE( ),INTERVAL 30 DAY) GROUP BY wpb_posts.ID ORDER BY meta_value LIMIT 0, 10
If I navigate ahead to next month, using the links at the bottom of the calendar widget, I get this:
SELECT SQL_CALC_FOUND_ROWS DISTINCT wpb_posts.*, meta_value as datetime, meta_id FROM wpb_posts JOIN wpb_postmeta ON wpb_postmeta.post_id = wpb_posts.ID AND meta_key=’_rsvp_dates’ WHERE 1=1 AND wpb_posts.post_type = ‘rsvpmaker’ AND ((wpb_posts.post_status = ‘publish’)) AND meta_key=’_rsvp_dates’ AND meta_value >= ‘2016-08-01’ AND meta_value < DATE_ADD(‘2016-08-01’,INTERVAL 30 DAY) GROUP BY wpb_posts.ID ORDER BY meta_value LIMIT 0, 10