IIUC, the most basic version is when you have a log where every entry has both “date added” and “effective date,” so you can add stuff to the log retroactively. For example, “the user just informed us yesterday that they moved last year” -> address date added=yesterday, date effective=last year

I have similar setup in Orgzly (kinda in Emacs too but it's buggy and not not as useful there) where a note has a "created time" property that's always automatically applied. And then there's the "closed time" applied when I set note the state to "done", which I sometimes modify depending on what the note is for and thus what "done" means.