By default Joomla will show a publuished for articles in this format...
Published on Wednesday, 19 March 2014 12:56
To change this format, you need to update the Language file. Joomla 2.5 makes this easy to do from the backend...
In the backend, go to Extensions -> Languagemanager -> Overrides.
Language Constant:DATE_FORMAT_LC2
Text (Default):l, d F Y H:i
Text (New):d F Y
See http://php.net/manual/en/function.date.php for date formats.
To remove the "Published on" bit, add a new Override
Language Constant:COM_CONTENT_PUBLISHED_DATE_ON
Text (Default): Published on %s
Text (New): %s
The resulting date should become...
19 March 2014