Does anyone else get a sense of vertigo when they try out numbers like 3000000000 (January 23, 2065)? It's like it's close enough to be tangible but far enough to be scary.
Interestingly, there is an error in your code: number of seconds in a year is not constant, so you might get next year before a new year.
Here's a fixed version: http://jsfiddle.net/r8txd/4/show/
I wanted the rate of time increase to be constant every year, and I wanted the time to be universal (across all timezones). I did take leap years into account by calculating the average year length in seconds. I also wanted the calculation to be simple and independent of variations in earth's rotation speed changes, etc. So yes, over a long time, it will diverge from "years" as we know them.
The only reason I used years is to provide context, since most people have a feel for how long a year is. After that, everything is base 10.
