I have Linux and in /etc/sysconfig/clock I readTIMEZONE="Europe/Berlin"

Env. Variable TZ LC_TIME* or TIMEZONE is not set.

On tools-sgebastion-10 wget -O - -q "https://de.wikipedia.org/w/index.php?title=Darwin_Mounds&diff=175806499&oldid=148646282" | grep ":33" shows 8:33 too, so it smells it is not my local system

If you open the "Developer Tools > Console" on a non-Wikimedia page in your browser and enter

(new Date()).toLocaleString("en-US",{weekday:"long",day:"numeric",month:"long",year:"numeric",hour:"numeric",minute:"numeric",second:"numeric",hour12:false,timeZoneName:"long"});

What is the output?

In case you use Firefox, is privacy.resistFingerprinting maybe enabled?

I can confirm the problem with the latest Google Chrome and the latest Firefox on Windows 10.

Firefox: Output is: "Wednesday, May 25, 2022, 15:01:39 Central European Summer Time"

privacy.resistFingerprinting = false

I tried this one with chrome and no login:

TZ=EST5EDT TIMEZONE=EST5EDT chromium "https://de.wikipedia.org/w/index.php?title=Darwin_Mounds&diff=175806499&oldid=148646282"
and in the Chrome-console I see: 'Wednesday, May 25, 2022, 09:13:34 Eastern Daylight Time' so it uses EST5EDT (according to the manuals the default)

However, when I am not logged in I see 8:33 which is one hour off to the correct 7:33

Same behaviour with
TZ=CET TIMEZONE=CET chromium "https://de.wikipedia.org/w/index.php?title=Darwin_Mounds&diff=175806499&oldid=148646282"
'Wednesday, May 25, 2022, 15:19:11 GMT+02:00'

And again 8:33 when not logged in.

Every browser, not only chrome! Even Lynx shows the same behaviour, the original report was based on Firefox.

It even happens in the labs environment ("tools-sgebastion") as shown above by Wurgl - it is no "local system" problem for sure.

Please replace "local system" with "browser software" in that case.

I just tried it with Google Chrome, with Brave, with Firefox, with Microsoft Edge and even with the Internet Explorer on a bog-standard Windows 10 PC. I tried it with Google Chrome on a Windows 10 Laptop and I tried it on two different Linux machines using wget. The problem was visible in every single test.

When you have a new created account (or when you never changed your settings of the timezone), you will see the same information as not logged in with one hour off for the other half of the year.

Once you set your timezone explicitly to e.g. Europe/Berlin, you will see the different times compared to not logged in.

However: for my example above: https://de.wikipedia.org/w/index.php?title=Darwin_Mounds&diff=175806499&oldid=148646282

$ sql de
MariaDB [dewiki_p]> select rev_timestamp from revision where rev_id in (175806499, 148646282);
+----------------+
| rev_timestamp  |
+----------------+
| 20151202063312 |
| 20180405153436 |
+----------------+

the first one shows an UTC-Hour of 6, the second hour is 15. The first one is has no daylight saving, since in december, the second one has daylight saving since in april. So in december I expect one hour off, whereas in April I expect is two hour difference.

I see not logged in "2. Dezember 2015, 08:33 Uhr" vs. "5. April 2018, 17:34 Uhr", so both show 2 hours offset.

Same on tools-sgebastion-10 with wget:
wget -O - -q "https://de.wikipedia.org/w/index.php?title=Darwin_Mounds&diff=175806499&oldid=148646282" | egrep ":33|:34"

"2. Dezember 2015, 08:33 Uhr" and "5. April 2018, 17:34 Uhr"

Again both with two hours offset.

So when you are not logged in (or with an account where you never changed the timezone settings) the daylight saving is simple ignored.

I think(!) the reason is some default value
https://de.wikipedia.org/w/api.php?action=query&format=json&meta=userinfo&ascii=1&formatversion=2&uiprop=options

This returns when logged in as Wurgl (with correct times) the following line "timecorrection": "ZoneInfo|120|Europe/Berlin",

When not logged in (or when I never changed the timezone, like in the Bot-Account APPERbot) I see "timecorrection": "System|120",