When a date is to be shown that is from this year it is shown as "Mar 12" for the "12th of March" rather than "Mar 12 '14".
While the full form is not what I'm used to (as a European) it is at least unambiguous. However "Mar 12" reads as "March 2012" to me and confuses me every time. Although I have (after months of pain) stopped misreading it I still feel the
Parse Error: Needs Stack Exchange Mode and the slight pause as my brain tried to reparse it.
The most recent example of someone confused by this is here Why inaccurate ''member for" info is shown in Stack Overflow. I was myself caught by this way back.
Even for recent dates; once the date is shown at all show the full date including the year. So this post was posted on Mar 22 '14.
This seems to have no downsides as it takes no extra space (there needs to be space for the long form anyway) and is much clearer to those of us who don't use an American date system.