There are two ways:
via php
## 2. in php
You can also use php code, as in the following way
(inspired from this page (https://stackoverflow.com/questions/3776682/php-calculate-age), and _slighty modified_:
$dob =”$row[anno_nascita]”;
$age = date_diff(date_create($dob), date_create(‘now’))->y;
echo “age: $age years
“;
via mysql in phpmyadmin
1.do this sql query:
select *,year(CURDATE())-year(anno_nascita) age from studenti__classi;
2. save the result as view
3. and so you will have, in the view, the age (of your students, i.g.) that can work in LibreBase (to connect with that view).