The schedule can be published the minute you have a speaker with an approved session. That will show up in your embed as a TBD planned session with no time set.
You can not fully build out a final schedule until you have all the content finalized.
Once you have the content finalized this is how to build out the schedule.
How the Auto Scheduler works
If you have 3 keynotes they will be schedule start / middle / end
If you have 2 keynotes they will be scheduled start/end
If you have 1 keynote it will be scheduled at the start
(over 3 keynotes the sessions would be added to the end as there is no logical schedule for over 3)
If you have an intro it will be scheduled first
If you have an outro it will be scheduled last
Sessions will follow and be placed inbetween the above rules
Sessions will be followed with an advert
Spotlights will follow sessions but will also follow a break if a break is due
Spotlights will be followed with an advert
Adverts will match session partners where an advert is available otherwise they will find an unused advert