<?php
$cal1 = IntlCalendar::createInstance();
$cal2 = clone $cal1;
var_dump($cal1->after($cal2), //false
$cal2->after($cal1)); //false
$cal1->roll(IntlCalendar::FIELD_MILLISECOND, true);
var_dump($cal1->after($cal2), //true
$cal2->after($cal1)); //false