With this pluging you can add a countdown to your blog. Just specify an end-date in the settings (backend) and put one single line of php-code somewhere you want this countdown to be displayed. This plugin uses the ajax-technology for updating the countdown every second. The moment you change the specified date in the settings, the plugin recognizes this change and updates itself according to the new date.

COUNTdown

This plugin allows you to add an ajax-updated countdown to your blog.

Toze

This plugin finds automatically the air date of the next episode of the TV show you choose and displays a countdown to it
<h3>Key Features & Options</h3>
TV show picker select your show from a database of more than 25.000 shows. 
Theme Dark and light theme.
<h3>Question & Supports</h3>
Please leave message for questions, supports or new features on next version here: 
http://support.tozelabs.com
This plugin is kindly (and freely) provided by TVShow Time (tvshowtime)

TVST Countdown

A plugin for displaying a countdown to the next episode of your favorite show. Perfect for the blogs related to a TV show.

COUNTdown vs TVST Countdown