Gary Jones

Can add multiple calendar widgets – each of them set to different categories (or All Categories).
The tooltip on the per-day links shows only post titles from that category, and when you click on the calendar link to bring up the day archive of posts, only posts from that category are shown.

Calendar Category

Un-registers the default Calendar widget, and registers a new one which supports showing only those posts in certain (or all) categories.

Masahiro NAKASHIMA

twinpictures

katanyan

rinoshiyo

nashiko

Installing this plugin allows you to adjust the behavior of the area below the posts screen category and custom taxonomy box.
<ol>
<li>Stop the checkbox from moving</li>
<li>Change checkbox to radio button</li>
<li>Make parent categories unselectable</li>
<li>Required to Category or Taxonomies</li>
</ol>

Adjust Admin Categories

Installing this plugin allows you to adjust the behavior of the area below the posts screen category and custom taxonomy box.

Calendar Category vs Adjust Admin Categories