Timezone bug in either rcube_utils::anytodatetime() or zipdownload::_download_messages()

[gurnec]

Prerequisites

• I have searched for duplicate or closed issues
• I can recreate the issue with all plugins disabled

Describe the issue

This is in regards to the zipdownload plugin's Export -> Mbox format. Each email in this format is prefaced by an arrival-time header:

From user@example.com Sat Apr 18 14:19:20 2026

The header doesn't include a timezone, but I believe the intent is for UTC?

In zipdownload, this line is formatted by:

roundcubemail/plugins/zipdownload/zipdownload.php

Line 238 in 018bcf7

$timezone = new \DateTimeZone('UTC');

roundcubemail/plugins/zipdownload/zipdownload.php

Lines 261 to 264 in 018bcf7

	$date = rcube_utils::anytodatetime($headers->internaldate, $timezone);
	if ($date) {
	$date = $date->format(self::MBOX_DATE_FORMAT);
	}

Which calls into rcube_utils::anytodatetime:

roundcubemail/program/lib/Roundcube/rcube_utils.php

Lines 1173 to 1188 in 018bcf7

	if (!empty($date)) {
	try {
	$_date = preg_match('/^[0-9]+$/', $date) ? "@{$date}" : $date;
	$dt = $timezone ? new \DateTime($_date, $timezone) : new \DateTime($_date);
	} catch (\Exception $e) {
	// ignore
	}
	}
	// try our advanced strtotime() method
	if (!$dt && ($timestamp = self::strtotime($date, $timezone))) {
	try {
	$dt = new \DateTime('@' . $timestamp);
	if ($timezone) {
	$dt->setTimezone($timezone);
	}

Typically, line 1176 above succeeds in parsing a string from IMAP, however if that string contains a timezone, the DateTimeZone('UTC') parameter is ignored. This is returned and format()ed by zipdownload without any timezone string, however the DateTime object still stores the originally parsed timezone, and the resulting string is in that timezone.

Note also that if the initial conversion in anytodatetime() fails and strtotime succeeds instead, the result is converted to the requested timezone on line 1187.

Should line 1187 apply to both cases in anytodatetime()? Should zipdownload call setTimezone() instead?

What browser(s) are you seeing the problem on?

Chrome

What version of PHP are you using?

v8.3

What version of Roundcube are you using?

v1.7-rc6

JavaScript errors

No response

PHP errors

No response