Comment by santiagobasulto

Yes. Time dilation (with respect of the stationary observed) is calculated using the Lorentz factor.

At 99.999% of C, the Lorentz factor is ~223.6.

It grows pretty quickly as you add more 9s to the fraction. Every two additional 9s multiply the Lorentz factor by ~10.

So at 0.99999999999 c, it'd be ~223,607x.

2.5M years / 223,607 is: ~11 years

Of course this is all highly theoretical.

https://en.wikipedia.org/wiki/Lorentz_factor