Event to update a column won't run
It seem that your event scheduler is not running causing the problem of event not getting executed. use following command to check 

show global variables like 'event_scheduler';


if you get that it is off, you can do if you are in MySQL 5.6 or higher

 set global event_scheduler=1;


or add the following line in cnf file to make this change permanent and in versions &lt;5.6

 event_scheduler=ON


The given code would work once you turn on the event scheduler using above approach.

Hope it helps.