I did a quick test and on my 64-bit linux box. gmtime and localtime max out in the year 2147483647 (with the next second after giving -2147483648 as the year). So to get much past 55 bits of time somebody will have to update the output routine to use a 64-bit int for the year instead of an unsigned 32-bit int. Hopefully somebody will take care of that bug sometime in the next couple billion years.