bug#40585: timezone offset issues primarily in qtwebenine

[divan@santanas.co.za]

Greetings :)

Having similar issues to https://issues.guix.info/issue/35746 but not
quite the same.

I'm having time offset issues in various applications on guix system.

My timezone is set to

(operating-system
 (host-name "swift")
 (timezone "Africa/Johannesburg")
 (locale "en_US.utf8")

Which in terminal is correct
ds@swift ~ $ date
Sun 12 Apr 2020 09:54:27 PM SAST

So I'm +0200, yet many applications report there time in UTC which is
frustrating.

Apps being:
- qutebrowser
- ungoogled-chromium

icecat works, when the privacy feature (ResistFingerprinting) is
disabled in about:config .

I was chatting to the maintainer of qutebrowser, str1ngs, on #guix and
he did not have the same issue on his guix system. Which is really
strange. He tried various debugging with me and in the end I think he
said:

  <str1ngs> divansantana and QDateTime works as well  [21:12]
  <str1ngs> it's something qtwebenine or javascript related

My locale, in case that's relevant:

$ locale
LANG=en_US.utf8
LC_CTYPE="en_US.utf8"
LC_NUMERIC="en_US.utf8"
LC_TIME="en_US.utf8"
LC_COLLATE="en_US.utf8"
LC_MONETARY="en_US.utf8"
LC_MESSAGES="en_US.utf8"
LC_PAPER="en_US.utf8"
LC_NAME="en_US.utf8"
LC_ADDRESS="en_US.utf8"
LC_TELEPHONE="en_US.utf8"
LC_MEASUREMENT="en_US.utf8"
LC_IDENTIFICATION="en_US.utf8"
LC_ALL=

I test the browser timezone via browsing to https://play.grafana.org/
for instance. But I've noticed the issue in multiple sites.

Perhaps this is a separate issue but in notmuch I notice similar:

In some emails it gives time in UTC
Date: Thu, 09 Apr 2020 12:55:21 +0000

While other emails it gives +0200 time.
Date: Sun, 12 Apr 2020 21:04:01 +0200