A funny consequence of this is that there are people alive today that do not know (and never will know) their exact age in seconds[1]. This is true even if we

A funny consequence of this is that there are people alive today that do not know (and never will know) their exact age in seconds[1]. This is true even if we assume the time on the birth certificate was a time precise down to the second. It is because what was considered the length of a second during part of their life varied significantly compared to what we (usually) consider a second now. [1] Second as in 9192631770/s being the the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom