Whenever I use relative dates, I usually draw the line at either one week or one month, after which I go to absolute dates. It can be cognitively challenging to see a date from two days ago and work out whether it was two days or one day, hey, today's Thursday right so that was Tuesday etc., whereas from 2012 a timestamp from 2009 isn't cognitively challenging to read as "years ago", and if you want the precision, it's there.

Personally when I've done it I often also simply always have the absolute time: "Wednesday, August 22nd at 8:22PM (a day ago)", with the order of the two elements chosen depending on which makes more sense.