Date_select and sessions


i am using date_select to allow someone to select their birthdate in a
form. however date_select uses 3 wierd labels in the forms like

1940 1941 .

and then the month is user[birthdate(2i)] and so on. My issue is i
dont know the best way to keep this data in a session (if there is a
user error on the form and want to keep data populated). Also if
someone wants to edit their birthdate later on after a find() call,
how is this stored and later parsed by the form ?