I’m not sure if this question is correctly tagged since you mentioned you’re using the Categories Widget. The tag is for the List Category Posts plugin.
Using the plugin, the first possible thing that comes to my mind is using the few available date parameters:
monthnum and year – List posts from a certain year or month. You can use these together or independently. Example:
[catlistwill list posts from the year 2015.
year=2015][catlist monthnum=8]
will list posts published in August of every year.[catlist year=2012will list posts from December 2012.
month=12]
This is not available on the widget (yet), but you could add it as a shortcode in your template file:
<?php echo do_shortcode("[catlist id=3]"); ?>