Update date time of page to current time when refreshing that page ?

Hi,

I am using theme twenty twelve.

How to update post date of page to current time when refreshing that page.

Example: I write a post on May 28, 2013. And now, when I refresh that post, it will change may 28 to June 8.

How to do this? Thank you very much !

This is code of date time in theme:

$date = sprintf( '<a href="%1$s" title="%2$s" rel="bookmark"><time class="entry-date" datetime="%3$s">%4$s</time></a>',
		esc_url( get_permalink() ),
		esc_attr( get_the_time() ),
		esc_attr( get_the_date( 'c' ) ),
		esc_html( get_the_date() )

and

// Translators: 1 is category, 2 is tag, 3 is the date and 4 is the author's name.
	if ( $tag_list ) {
		$utility_text = __( 'This entry was posted in %1$s and tagged %2$s on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
	} elseif ( $categories_list ) {
		$utility_text = __( 'This entry was posted in %1$s on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
	} else {
		$utility_text = __( 'This entry was posted on %3$s<span class="by-author"> by %4$s</span>.', 'twentytwelve' );
	}