app/Individual.php
public static function birthDateComparator(): Closure
    {
        return static function (Individual $x, Individual $y): int {
            return Date::compare($x->getEstimatedBirthDate(), $y->getEstimatedBirthDate());
        };
    }
public static function birthDateComparator(): Closure
    {
        return static function (Individual $x, Individual $y): int {
            return Date::compare($x->getEstimatedBirthDate(), $y->getEstimatedBirthDate());
        };
    }
public static function birthDateComparator ( ) : Closure { return static function ( Individual $ x , Individual $ y ) : int { return Date :: compare ( $ x -> getEstimatedBirthDate ( ) , $ y -> getEstimatedBirthDate ( ) ) ; } ; }
A closure which will compare individuals by birth date.

@return Closure
A closure which will compare individuals by birth date .