I don't care about the "real" age or birthday. It's just another series of digits. I do care about the "official" age, assuming it's a consistent birthday for each performer. I.e. Yuma Asami (a long timer performer who still has a girlish look) wouldn't just arbitrarily lose 10 years from her official age since she was still bankable as a school girl. If the studios are half responsible about it (and in the internet age, it's a little harder to change your lie), then whatever fake age they gave to her when she debuted, that's the number they are stuck with. Rather than waste time thinking or fretting over her mystery real age, I'm happy to reference her official age, the same way we treat age/birthdays for all celebrity anyway.
The internet really needs a JAVpedia. Would be great if wikia allows adult contents. I did seriously consider using whatever features available on Akiba Online to build something like this. The official statistics, a reasonably complete filmography, whatever tidbits that can be scrapped from reasonably reliable sources such as the Japanese wikipedia and if there's someone obsessive enough to support it, to follow a performer's social media account and pull suitable data or info into her page.
Of course being a tech geek, I would like to see advanced search which would definitely include search by age or birthday (range) and also boolean search: e.g. find all JAV actress born before 1990/06/01, debuted after 2012/01/01, made more than 10 AV's and with a cup size of C or larger. Or find all actress who have made at least 2 AVs (not counting compilations) each year for 10 years in a row.