Conditionally display elements based on time frame?

Conditionally display elements based on time frame?

I'm new here so excuse me if I seem ignorant or the question is confusion
or it's not appropriate here.
I want to have a block on my website to have flash animations, images or
other html elements. For example, you could see this site HERE ; they have
flash animation on their header.
Yet, I want to display a Christmas Photos in 25th December. In 14th
February, I want to display flash animation of Valentine coditionally, so
on and so forth.
Could I achieve this function in pure PHP scripts (prefer) OR Joomla? If
yes, how could I do it?
Thanks!
SVR