Using the 2013-07-08 client, I've gotten character deletion to work again,
from this ticket:
http://rathena.org/board/tracker/issue-7970-character-deletion-time/
Modifying the source with the change at the bottom of that ticket will fix the issue of the client showing some date at the end of ~this year.
Additional Note: The required format for the birthdate (for anyone who runs into this issue) is YYMMDD, no dashes.
The current value in the msgstringtable is incorrect.
All of that aside:
When I delete a character, I get a message that says 'Please Wait', and it hangs on that message indefinitely, requiring that I close my client and re-open it.
The character does successfully delete, but is there something that can be done about this issue?