From what I can gather from the wiki, it seems like the Compact Columns plugin can be indeed configured to display only the absolute build time (see also this screenshot).
I'm still planning to implement it into the extra-columns plug-in, because it's actually already half-way in there anyways.
My plan is to split up the "Build Duration" column and create a separate "Build Start" column,
which can then be configured to show the build start either relative ("2h ago") or absolute (e.g. "2013-12-21 10:00:00").
So I'm merely adding the option to show the absolute time instead of the relative time.
And I think compared to the Compact Columns plugin it would definitely be a more straight forward solution to meet this requirement.