Board Thread:General Discussion/@comment-4129195-20151107164301/@comment-8865495-20151107165239

First off, setting a class does pretty much nothing other than applying whatever styles found in .countdowndate "section" of MediaWiki:Common.css, MediaWiki:Wikia.css, and/or MediaWiki:Monobook.css. However, using JS, you can select 'span's with the class "countdowndate" and replace the html of it with a fully functional countdown timer thing.

Edit: http://mindgrader.com/tutorials/1-how-to-create-a-simple-javascript-countdown-timer This site has good enough instructions to make a countdown