DateTimeImmutable (and DateTime) modify does not respect Daylight Saving Time shifts

[karptonite]

Description

The following code:

<?php
date_default_timezone_set("America/Chicago");

$startDate = new DateTimeImmutable( "2024-11-01" );
var_dump( $startDate );
$endDate = $startDate->modify( '+72 hour' );
var_dump($endDate);
$otherEndDate = $startDate->add( new DateInterval( 'PT72H' ) );
var_dump( $otherEndDate );

Resulted in this output:

object(DateTimeImmutable)#1 (3) {
  ["date"]=>
  string(26) "2024-11-01 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(15) "America/Chicago"
}
object(DateTimeImmutable)#2 (3) {
  ["date"]=>
  string(26) "2024-11-04 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(15) "America/Chicago"
}
object(DateTimeImmutable)#4 (3) {
  ["date"]=>
  string(26) "2024-11-03 23:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(15) "America/Chicago"
}

But I expected this output instead:

object(DateTimeImmutable)#1 (3) {
  ["date"]=>
  string(26) "2024-11-01 00:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(15) "America/Chicago"
}
object(DateTimeImmutable)#4 (3) {
  ["date"]=>
  string(26) "2024-11-03 23:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(15) "America/Chicago"
}
object(DateTimeImmutable)#4 (3) {
  ["date"]=>
  string(26) "2024-11-03 23:00:00.000000"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(15) "America/Chicago"
}

Note that the from 11-1 to 11-4, Daylight Saving time ends. If you change the time by adding a DateInterval, it gets it right, but it gets it wrong with modify. Also note that if instead of adding 72 hours, you add 3 days, the inconsistency goes away--DateInterval understands, apparently, that one of those days is 25 hours, and adjusts correctly (at least, it seems correct to me) to Midnight on 11-4.

PHP Version

PHP 8.3

Operating System

No response