in src/datetime/Time.php [398:410]
public function plus(this $other): this {
if ($other->isZero()) {
return $this;
} else if ($this->isZero()) {
return $other;
}
return self::fromParts(
$this->hours + $other->hours,
$this->minutes + $other->minutes,
$this->seconds + $other->seconds,
$this->nanoseconds + $other->nanoseconds,
);
}