Depends on what you are asking
If you are saying you don't want to live stream, instead ask Facebook to play/stream a video at a set time, yes that is something that Facebook can do. You can use OBS to compile/compose/create the video, or use anything/something else.... it depends on what you are trying to accomplish as to which tool makes most sense
Then upload video to Facebook to your library (make it Private). Then follow Facebook instructions for streaming it at a specific time (becomes Public, or something like that).
There are options to auto start OBS from a scheduled task, and perform certain actions... but there all kinds of potential for issues that complicate matters if you already have the video created that you wanted streamed. To me, seems like over complicating matters to get OBS involved for streaming at a scheduled time, when Facebook (YouTube, and others) have native mechanisms to handle your request. And the benefit of not having to worry about video upload/Internet connection at the time of streaming.
But lots of ways to handle this... it depends. Hopefully this helps give you another way to approach solving your problem
