caldav php client - get free time

one text

Good morning ! :)

I am "building" a php calDAV project with this code: https://github.com/wvrzel/simpleCalDAV

All works fine ! I can create / modify / delete / get events from my own calDAV server (Synology Calendar on Synology NAS)

But now, I would like to start a query to get only the free time slots. With this code I get all events from now to the last day of next month.

$getEvents = $client->getEvents(date('Ymd').'T000000Z', date("Ymt", strtotime(date("Ymd",strtotime("+1 month")))).'T000000Z');

Can you help me please? Tanks !