Tính thời điểm mà ai đó đã sống được 10 ^ 9 giây

Calculate the moment when someone has lived for 10^9 seconds.

A gigasecond is 10^9 (1,000,000,000) seconds.

Code:

<?php

function from(DateTime $birthday)
{
    $birthday = clone $birthday;
    $gigaSecond = new DateInterval(sprintf('PT%dS', 1e9));
    $birthday->add($gigaSecond);

    return $birthday;
}