As far as I know, COA can't display dates earlier than 1901-12-13, because of UNIX problems. Any dates earlier than 1901-12-13 seem to be replaced by 1970-01-01. UNIX programs are usually only able to handle times between 1901-12-13 20:45:52 and 2038-01-19 03:14:07, causing problems with some early dates of birth. Check the dates of birth for Walt Disney, Ub Iwerks, CB, Elizabeth Beecher, EDu, DHe and other people and you'll see that they were all born on "1970-01-01" according to COA.
I don't know if NHH might want to move early dates to some comment field as a temporary or permanent solution. Listing only a year in the "date of birth" field seems to work even if the year is before 1901, as you can see by looking at the page about TOs.
I don't know if HF might want to make DIZNI complain about too early (or too late) dates. I'm not sure if there is a trivial solution on the COA side since the problem lies in background programs (PHP, MySQL or both). It might be better to avoid them altogether (by listing just a year and adding the full date to a comment field). After all, it only affects a small number of dates of birth in Inducks.
Solved, however all translations need to be changed, because I'm using another PHP date/time package.