When a free-busy calendar rendition is requested using the get_freebusy command, private events and todos are included or excluded depending on the value of the transparent parameter stored with the events and todos when they were created or modified.
Using either storeevents or storetodos, to keep the event private, set the event or todo parameter to transparent=1. Set it to transparent=0 to allow the event or todo to be included in the free-busy calculation.
As opposed to regular events, all-day events (isAllDay=1) default to private and transparent (transparent=1). For the all-day event to be included in the free-busy calculation, set the parameter to transparent=0.