It shows entries/posts around today's date in the past (if they exist). It is highly customizable.
[ Notas en castellano en la web ] [ Notes en catala a la web ]
It shows around this date entries/posts in the past (if they exist). It is highly customizable. By default it retreives a week around the current day 1 year ago.
IMPORTANT: If your sidebar supports the new WordPress Widgets, you might better use the "Around this date in the past... - Widget Edition" plugin. Check-it here: [ http://wordpress.org/extend/plugins/plugin/around-this-date-in-the-past-widget-edition/ ]