Where is the Delayed/Schedule Post code in WP?

Not looking for anything complex, just the file/path to the file of the code that allows the user to create a delayed/schedule post.

Specifically as shown (http://en.support.wordpress.com/posts/schedule-a-post/).

I’m looking at Page.php and Cron.php (and others) but nothing specifically stands out as the code on the UI/processing side of the link I posted — I see related methods, but not the choosing of the date/future time and the sorting into the DB.

Thanks in advance