Mysql query - Event to delete rows by its value
To fix the syntax error:

DELETE FROM events WHERE check_in &lt; (NOW() - INTERVAL 1 DAY)


That won't land on midnight.  Instead change to:

DELETE FROM events WHERE check_in &lt; CURDATE() - INTERVAL 1 DAY


Give writing the EVENT a try.

Be sure to do (once):

SET event_scheduler = ON;