This post may help you...
http://forums.b2evolution.net/viewtopic.php?t=18235&highlight=date

I read the post before sending mine.
It does nto apply to nifty corners.

Ok.. so try replacing the date format code you have with one form another skin...
eg:

<?php
				$Item->issue_time( array(
						'before'      => '<h2>',
						'after'       => '</h2>',
						'time_format' => 'M j, Y',
					) );
			?>

Where are you seeing ['#'] ?

@EdB from Nifty...

<?php
	// ------------------------------ DATE SEPARATOR ------------------------------
	$MainList->date_if_changed( array(
			'before'      => '<h2>',
			'after'       => '</h2>',
			'date_format' => '#',
		) );
	?>

@John: That's what I figured, which means the linked post is the answer. Especially the links provided by filthio - the second one seems particularly cool.

@michael: you change the date_format to whatever format you want it to be (within the boundaries that php defines for date formatting).