src/Khayyam/Khayyam.php
public function diffInYears(Carbon $dt = null, $abs = true)
    {
        $dt = ($dt === null) ? static::now($this->tz) : $dt;

        return (int) $this->diff($dt, $abs)->format('%r%y');
    }
public function diffInYears(Carbon $dt = null, $abs = true)
    {
        $dt = ($dt === null) ? static::now($this->tz) : $dt;

        return (int) $this->diff($dt, $abs)->format('%r%y');
    }
Get the difference in years

@param Carbon  $dt
@param boolean $abs Get the absolute of the difference

@return integer