That’s a good question. My hiearchy idea was specifically for uncertain facts when all you say about the fact is that ‘well it was within 5 years’ or, ‘it was longer than a year ago’. The case you’re talking about is that you have some relatively concrete information so maybe that’s simply a history_of + value_as_concept + number_as_value (in days)…
When I think of the concepts and concept hierarchy, I’m thinking categorical data, so I would say you just put the historical fact into a category and the problem I am seeing in your example is that the value in question could fall into 2 categories: within 5y, later than 1y and my first reaction is to prefer ‘within’ time periods and not ‘after’…Or perhas the solution is to drop 2 observation records one for each bonding window of hiearchy, so you can say if you want to find things between 1 and 5 you say 'must find an observation within 5 and must find an observation of after 1 yaer.
I totally understand the attraction of having those derived ‘range of history’ since it does seem to make sense…
Maybe the alternative is to have a dedicated ‘history’ table that acts like observation, but it has min_days and max_days that let you specify a range of where this event occurred relative to the ‘fact date’.