readability - When should a year be added to a timestamp?

Stack Exchange uses relative timestamps to indicate when an action occurred; a question was asked, edit was made etc. This is done as far back as "2 days ago"; anything prior to exactly 48 hours ago uses the full timestamp. If the timestamp is not in the current year it includes the year.

However, with the advent of a new year this seems to create a dissonance between dates, which occurred exactly two days ago as they jump from "2 days ago" to last year.

This screenshot was taken at 13:23:55 (UTC). I used Stack Overflow as it has the most questions but it's true for all Stack Exchange sites.

As 2012 was last year the year has been added to the timestamp, which makes it seem, to me, that the question was asked longer ago than it actually was.

If there's no need to include the year is it more understandable for a user to not see it? I.e. if it is the 20^th June 2013 should the timestamp for dates after 20^th June 2012 not include the year portion?

Answer

Your proposed solution also introduces a jump. If it's 20 June 2013, and I see a post dated “22 June”, I'm going to think “June this year”, and then do a double take because that's still into the future. When it's June 2013, all posts from June 2012 should be marked “June '12”. As the end of the month approaches, it may be good to mark posts from July as being from the past year as well.

I think anything from keeping the previous calendar month yearless to keeping the past 10 calendar months yearless would be reasonable. That way, “Dec 29” still looks like a recent date in January, but a post that's 11 months old has the added year as a mark of age.

Unix (I know, not a common reference in a UX context) does something like this when showing file times: files dates in the last 6 months are displayed with month, day, hour, minutes while older files and dates in the future are displayed with year, month, day. This has the downside of making exactly-6-months-back a jump, I think it would be better to align the jump with a calendar month change.

Not that it's a big deal — whatever you do, there's a jump (from X days ago to a calendar date).