什么是PHP datetime可以表示的最旧和最新的日期？

Let's assume a 64 bit version of PHP in case that matters

I'm thinking about generating a random datetime but I realised I don't know how far back in time or how far forward in time the min-max possible values for datetime are to use as min-max for random

<?php

$min = \date_create('@' . PHP_INT_MIN);
var_dump($min->format('Y-m-d H:i:s'));

$max = \date_create('@' . PHP_INT_MAX);
var_dump($max->format('Y-m-d H:i:s'));

$diff = \date_diff($min, $max);

echo $diff->format("%R%a days");

https://3v4l.org/8N17M

This is the earliest and furthest datetime I've found so far

Not sure why I'm getting 0 days in the diff though