Date dependent content with Server Side Includes 
Today I had to update a static website to show some xmas content in December. As I am a lazy guy, I searched for an option to show the content somehow automatically as soon as it is December and to stop displaying it in January.
Because that site is a simple static hosted website with only SSI available, I checked on SSI capabilities and inlcuded the content as follows:
<!--#config timefmt="%b" -->
<!--#set var="month" value="$DATE_LOCAL" -->
<!--#if expr="$month = Dec" -->
<!--#include file ="xmas.html" -->
<!--#endif -->
With some more tweaks you could rotate the look (e.g. with different css files) and content of your static website in regular intervals without too much work involved.