A Zen Blog Master Page defines the standard side columns for all blogposts that use it.
Master page side columns can only be edited from this page.
The blog calendar will automatically be inserted in whichever column exists, favoring the right column. If no columns are defined on this page, a right side column will be displayed so the calendar will have a place to live. Content in this middle column will not appear anywhere else. Your blogpost contents will replace this center section.