I'm not quite sure I understand the subject. 

But if indeed I understand what we are trying to say, then why not use:

{loS maH ben jIbogh. ngugh..}

forty years ago I was born. then..

or

{loS maH ben jIbogh. qaSpa' wanI'vam..}

forty years ago I was born. before that event (i.e. my birth) happened..

The question is, how would you describe an event at a time a known period before or after an event whose time was NOT known?

How would you describe ten years before he was born if you don't know when he was born, but you do know the event happened ten years before that?

-- 
SuStel
http://trimboli.name