PHP-s strtotime() will probably handle them all, even though it will make you cringe a bit. I never understood why simple integer unix timestamps are not more

PHP-s strtotime() will probably handle them all, even though it will make you cringe a bit. I never understood why simple integer unix timestamps are not more prevalent in API-s? Or some monotonic count from any reasonable epoch, depending on the context. How many APIs really have to ever return dates predating unix?