These docs are for an old release. Info on upgrading to v4
edit doc

eventMouseout

Triggered when the user mouses out of an event.

function( event, jsEvent, view ) { }

event is an Event Object that holds the event’s information (date, title, etc).

jsEvent holds the jQuery event with low-level information such as mouse coordinates.

view holds the current View Object.

Within the callback function, this is set to the event’s <div> element.

eventMouseout will not be triggered for background events.