On the 31st the number of the next month is calculated incorrectly

I think this is also UTC / local time zone related

I don't think that its timezone problem. I change topic. Now in pager 3 dates. If today is March 31st, then 5th month displayed twice.

Could you reproduce this on a new Drupal installation, e.g. on simplytest.me ? Do you patch something in date_pager? Or Javascript changing content in frontend? What is the URL in the false 05 link?
I couldn't reproduce it with the steps given above on simplytest.me.

Can simplytest.me choose "current" date?
No, i don't patch date_pager.
Same trouble in Claro or Olivero theme. Screenshot:

Both 05 links linked to May i.e. /view-url?date=2025-05.
On March 31st it's also possible to come in to April i.e. to /view-url?date=2025-04, but this 04 link is missing in pager.

I could reproduce it locally. It was a problem on top of the timezone problem with the mapping of the current date to the dates in the pager. Please test and review 🐛 Paging seems to be done using UTC and not local time zone. Active

Installed the latest version 2.1.1-beta1 . The problem is still there.

@vasyok : I cannot reproduce this issue, if I set the time manually to 31.3.2025. Which system timezone and user timezone are you using? Which field type is your date field?

I don't know why, but the results now are different from the results of my last answer. Sorry if I messed something up.

List of events is the same as before:

View is also the same:

System timezone and user timezone

/admin/config/regional/settings

Default country: Germany (If I switch it to "Ukraine" nothing changes)
Default time zone: UTC
Users may set their own time zone OFF

I wrote a function that defines 3 variables

• site_time
• site_timezone
• server_time

MYTHEME.libraries.yml

function MYTHEME_preprocess_views_view(array &$variables) {
  $date = new \DateTime('now', new \DateTimeZone(\Drupal::config('system.date')->get('timezone.default')));
  $variables['site_time'] = $date->format('Y-m-d H:i:s');
  $variables['site_timezone'] = $date->getTimezone()->getName();

  $server_time = new \DateTime();
  $variables['server_time'] = $server_time->format('Y-m-d H:i:s');
}

... and displayed these variables in the view page

views-view--MYVIEW--page-3.html.twig

Current site time: {{ site_time }}
Site time zone: {{ site_timezone }}
Server time: {{ server_time }}

Results

2.1.1-alpha2 without patches

If today is March 30th, the pager on /test-page is displayed correctly:

If today is March 31st, Maн is displayed twice:

2.1.1-beta1

If today is March 30th or 31st - May is not displayed:

Users may set their own time zone OFF does not mean that the website timezone is used, the users simply cannot change the settings via UI. I assume there was a different timezone set. Now the user time zone defaults to website timezone if user timezone is not configurable. Please review MR