Blogs that focus on timeless content should archive the posts by categories. Calendars and monthly archives are not optimal since the reader is not able filter the posts by the topics of his interest.
That being said sometimes a comprehensive archive where all the posts are listed, month by month, can be useful. Maybe the reader is looking for something that was written two weeks ago, or maybe he wants to grasp all the older posts from your blog.
The best solution for this problem is a WordPress plugin called Clean Archives. You just need to upload the plugin, activate it and drop a line of code on the page that you want the archives to be displayed. You can see the plugin working here.