My guess would be JavaScript that just has some functions built in and doubt it is very accurate. That is pretty interesting to watch though.
Basic javascript - there are lots of statics such as "someone dies every 10 seconds" - it is therefore a simple calculation to say how many people approximately have died in a day etc
You might want to take a look at some JavaScript tutorials. Math formulas aren't really that hard compared to all the other things you can do with JavaScript. There might even be some pre-written scripts/tutorials on some basic math functions. You would then just have to find the exact stats on how fast the population grows and so forth. Good luck!
Not sure how they did it but I ranked their web site using www.websnap.name . Nice concept. I like it.