Slide-By-Slide Animations: Traditional Countdown
http://pptheaven.mvps.org/tutorials/countdown.html

Tohlz, Shawn
PowerPoint Heaven
2005

Abstract:

In this tutorial, you will learn how to create a simple traditional countdown animation in 5 slides (I normally call it a Slide By Slide animation). This is achievable in a single slide (Stacking animation), but to reduce the difficulty, I will show you a simple one which can be editable easily at a later time.