Also for those born decades ago (40 or more years) the S. Koreans have two birthdays. The infant mortality rate was very high so they wouldn't register the birth until the child had grown up a bit. then the parents had to make a long trek to the register's office, often by, horse and cart or other questionable travel means, where the kid would get an official date. but the parents also had an approximate date of the actual birth that would follow that person also.