Coming Soon Page / Timer

I’ve tried using the original html code in a text block to get a countdown timer on my site similar to demo coming soon page, but it doesn’t work.

[tminus style="fortuna" t= "15-12-2015 12:45:05"]HTML to be displayed when the countdown reaches zero.[/tminus]

The code above is what I used. Is there another block of html or css code that I need in addition to this?