Time (and therefore dates) depend on what reference frame you measure them in. Einstein taught us this with his theory of special relativity. So sure he was born on 14th of March 1879 to us slow moving boring people on Earth, but if you had spent the last 133 year (as measured on earth) in a spaceship travelling close to the speed of light. Time would move much slower for you and when you returned to earth much less time (in earth years) would have passed since Einstein was born for you. (something like 20-30 years depending on your speed). So it is really hard to know how long ago Einstein was born without knowing what reference frame you are measuring time in.
Although, the inaccuracies in time keeping due to our georgian(?) date system are a lot larger than compared to any relativistic effects we experience on earth (gravitational, rotation of the earth, flying in an airplane…). What the heck is with leap years?! Just shoddy calendar design, if you ask me.