PHP DateInterval天数不一致

请使用以下PHP代码:

<?php
$timezone = new DateTimeZone('UTC');
$startDate = new DateTime('2022-09-26T00:00:00', $timezone);
$endDate1 = new DateTime('2023-02-28T00:00:00', $timezone);
$endDate2 = new DateTime('2023-03-01T00:00:00', $timezone);
$interval1 = $endDate1->diff($startDate);
$interval2 = $endDate2->diff($startDate);
print_r($interval1);
print_r($interval2);

下面是输出结果:

DateInterval Object
(
    [y] => 0
    [m] => 5
    [d] => 2
    [h] => 0
    [i] => 0
    [s] => 0
    [f] => 0
    [weekday] => 0
    [weekday_behavior] => 0
    [first_last_day_of] => 0
    [invert] => 1
    [days] => 155
    [special_type] => 0
    [special_amount] => 0
    [have_weekday_relative] => 0
    [have_special_relative] => 0
)
DateInterval Object
(
    [y] => 0
    [m] => 5
    [d] => 5
    [h] => 0
    [i] => 0
    [s] => 0
    [f] => 0
    [weekday] => 0
    [weekday_behavior] => 0
    [first_last_day_of] => 0
    [invert] => 1
    [days] => 156
    [special_type] => 0
    [special_amount] => 0
    [have_weekday_relative] => 0
    [have_special_relative] => 0
)

谁能解释一下，为什么第一个间隔的y-m-d是0-5-2，而days计数是155，而第二个间隔的y-m-d是0-5-5，即使只加了一天(实际上days的计数是156)？

我试着将相同的代码移植到其他语言中(确切地说是JavaScript和python)，第一个时间间隔的结果与PHP的相同:5个月零2天. 然而，第二个间隔的结果是5个月零3天(正如我所期望的那样)，而不是PHP所说的5个月零5天.