@
(you need an account to see links)
After so many days, an inactive account will automatically begin asking for the birthday with the password.
So, when you get to that page, type in a random birthday and try it.
It will then tell you invalid birthday and password, or just one of them. That's how you know.
As @
(you need an account to see links) said, that will be the URL if it's just an invalid birthday.
As for the information, there are soo many possibilities that way, sorry.
To create an algorithm simply to try all of them would be crazy.
However, if you are NFs with the user and can see the age, then I suggest figuring the possible two years.
I wouldn't want to try guessing a birthday continuously for months (which is what it would take) because TNT will probably flag the account.
They do keep records for how much a birthday and password are attempted, and so the account may get frozen for suspicious activity.
Therefore, instead of guessing, just watch the account on your NF list for when it changes age.
This is if you have a lot of time, but it's the best way if you don't want to flag the account by guessing or buy a birthday crack.