>>2185991Except the same VA also Does Yui and Pen-Pen, so it's probably one of their birthdays.
It would probably be hard to even define a birthday for Rei.
The day the current clone was activated? (For Rei III, this should be somewhere in December) The day the FAR made Lillith? The day Yui vanished, or when the failed salvage resulted in those mysterious "remains" Rei was made of? Any arbitrary point between transforming these into Rei I or them being used as base material somehow? How did they make her, even? If she was grown in a vat and developed like a normal fetus, albeit accellerated, you could take the time period she reached the developemental maturity of a newborn, but babies might be born later or earlier, so "newborn maturity" would be an interval, not a speciic date.