The format of the pubDate is dependent on the newsfeed source.  However, you can use XSL to take a substring of it, if the module you are using allows custom XSL transformation to be used.  I don't anything about the Orizonti NukeNews module, other than the developer has a good reputation for answering questions about his module.  Best bet is to check with the developer.

Now, if you can use a custom XSL stylesheet, the code is not that difficult, but you will need to make some assumptions after reviewing the source newsfeed.  For example, what is the actual data being generated by your newsfeed source?  Once you determine the format, you can use XSL to code for the format of choice, assuming that the newsfeed source will not change it's pubDate data format, or at least test for it, and revert to a fallback of just showing it, if your test fails.

Google for keywords "RSS" "pubDate" "formating", and you'll come up with many suggestions and coding examples of how others are doing this type of task.  Here's one that is pretty comprehensive with examples you can probably tweak to your situation.

http://geekswithblogs.net/workdog/archive/2007/02/08/105858.aspx

Cheers