t1gr0u

The plugin allows to change theme (template) on desired dates. 
If you want a Christmas theme automatically on your blog just for 5 days (or more), the plugin will do it for you.
Just enter a start date, an end date , select times and the theme which you want to use, that’s it.
You can have as many combinations as you wish.
A theme for each seasons, halloween theme, christmas theme… or even a day and night theme…
<h3>Admin Panel</h3>
The admin panel will allow to move re-order your theme changes. 
Just remember that, the top is the lowest and the bottom is the highest level. 
So, if you have a theme change (‘theme1’) set for the 23/07 – 01/08 first and theme change (‘theme2’) for the 24/07 – 26/07, and today’s date is 24/07, 
‘theme2’ will be displayed unless you move down ‘theme1’.”
The rules, which you have created, will stay year on year.

WP Change Template

The plugin allows to change theme (template) on desired dates.

vercalendario-info

This plugin creates widget which shows useful moon information such as the phase and visibility.
For more information about the mon calendar, please visit <a href="http://www.vercalendario.info/en/about/extensions/wordpress/install.html#currentmoon" rel="nofollow ugc">http://www.vercalendario.info/en/about/extensions/wordpress/install.html#currentmoon</a>.

Current Moon Information

This widget calculates the moon phase and its visibility either from the northern or southern hemisphere.

WP Change Template vs Current Moon Information