Check on Date calculation | WordPress.org

Hello @albertobellipario

Thank you very much for using our plugin.

Assuming the date field is the fieldname1, you can insert a calculated field in the form and enter the equation:

(function(){
var d = DATEDIFF(TODAY(), fieldname1, 'yyyy-mm-dd', 'y')['years'];
if(8 <= d) {
return 'Ehi, the difference is too much!';
}
return d;
})()

Best regards.