I am bulding a view with stats for users that are registred and inputed DOB. Currently core profile module and views (drupal 6) don't play along when using dates. The way data is stored seems to be the problem. Anyway you can't filter and sort your users by date, but you can make this happen with customfield PHP code. You get current year and DOB year from user like this and just calculate and you will get age of user, which you can then sort with table view if it is in customfield.
$datum=unserialize($data->profile_values_profile_rodjenje_value);
$age=date("Y")-$datum['year'];
print $age;