app/Date.php
public function addYears(int $years, string $qualifier = ''): Date
    {
        $tmp               = clone $this;
        $tmp->date1->year  += $years;
        $tmp->date1->month = 0;
        $tmp->date1->day   = 0;
        $tmp->date1->setJdFromYmd();
        $tmp->qual1 = $qualifier;
        $tmp->qual2 = '';
        $tmp->date2 = null;

        return $tmp;
    }
public function addYears(int $years, string $qualifier = ''): Date
    {
        $tmp               = clone $this;
        $tmp->date1->year  += $years;
        $tmp->date1->month = 0;
        $tmp->date1->day   = 0;
        $tmp->date1->setJdFromYmd();
        $tmp->qual1 = $qualifier;
        $tmp->qual2 = '';
        $tmp->date2 = null;

        return $tmp;
    }
public function addYears ( int $ years , string $ qualifier = '' ) : Date { $ tmp = clone $ this ; $ tmp -> date1 -> year += $ years ; $ tmp -> date1 -> month = 0 ; $ tmp -> date1 -> day = 0 ; $ tmp -> date1 -> setJdFromYmd ( ) ; $ tmp -> qual1 = $ qualifier ; $ tmp -> qual2 = '' ; $ tmp -> date2 = null ; return $ tmp ; }
Offset this date by N years, and round to the whole year.

This is typically used to create an estimated death date,
which is before a certain number of years after the birth date.

@param int    $years     a number of years, positive or negative
@param string $qualifier typically “BEF” or “AFT”

@return Date
Offset this date by N years and round to the whole year .