From their about page:
> The Long Now Foundation uses five-digit dates, the extra zero is to solve the deca-millennium bug which will come into effect in about 8,000 years.
> The Long Now Foundation uses five-digit dates, the extra zero is to solve the deca-millennium bug which will come into effect in about 8,000 years.
500 billion years is barely half way through the star forming age of the universe.
Dark era starts in 10^106 years time, or about 10^157 plank times, so any time can be respresented in 20 bytes.
Just 44 bytes will allow encoding of any point in spacetime, and they are using far more than that to simply encode years.
>2.4.2 Transcending Environmental Considerations
>However, we might get lucky. So, Y10K dates are able to represent any possible time without any limits to their range either in the past or future.