html5 has a <time> element. It carries the semantics noting that the contents are a date, and if the contents aren't in a set of machine readable formats there is a datetime="" attribute that can contain a machine readable format.
So eg: <time datetime="2011-11-12T14:54Z">November 12, 2011 6:54 PST</time> displays the date in a human readable format in PST while also noting the date in a machine readable time format.
It's possible some user agents may add support for functionality that takes advantage of these semantics. For example they may provide a display of the time in the user's current timezone. <time> is also used in some microdata formats iirc
pubdate seams to have been removed from <time>. Even if it's added back we probably should strip it out of WikiText since inline text shouldn't be able to define what looks externally to be authoritative information about the entire page that MW defined.
We should permit the use of <time> inside WikiText.