In garden/vanilla2, when I created a demo account so that people will be able to chek out the theme made by my wife (on more pages than what guest are able to view), I tried to leave out the birthday info, it was not possible. Then I tried to set it to 3 days ago (the date she started the theme), but I got a message stating I needed to be older than 16 yo.
It's seems to be in there:
library/core/functions.validation.php: // The minimum age for joining is 16 years before now.
1. Why is there such a limit? And if it's required, maybe it would be a good idea to put the value into a parameter.
2. Or maybe drop altogether the requirement for choosing a birthdate.