Is it possible to update Facebook Timeline using some sort of an API?
Say for instance if I wanted to upload a large amount of content for the reverse chronological history of the timeline?
See: Facebook Graph API reference at "Publishing":
You can publish to the Facebook graph by issuing HTTP POST requests to the appropriate connection URLs, using an access token.
For more detailed information, see also Graph API reference for a single "post".
Disclaimer: I haven't tried this myself, so there could be some limitations I'm not aware of.