I think the best way to display date/time is to have the text in relative date/time and title in actual date/time.
For example:
This post was made <span title="2012-08-23 2 PM EDT"> 2 hours ago </span>
This solves the problem of both clutter and practicality. Now whenever you need to know the absolute time, just hover over the relative time and it will also show up in screenshots!!
Doesn't help for multiple <span>s (actually <abbr>s from the post) in a single screenshot, but a bookmarklet or userscript that replaces all <abbr>s with their title attributes would help.
