Arch Linux

Full backtrace please

Starting program: /usr/bin/qt5ct
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/usr/lib/libthread_db.so.1".
[New Thread 0x7ffff19c8700 (LWP 2161)]
Configuration path: "/home/USER/.config/qt5ct"
Shared QSS paths: ("/home/USER/.local/share/qt5ct/qss", "/usr/local/share/qt5ct/qss", "/usr/share/qt5ct/qss")
Shared color scheme paths: ("/home/USER/.local/share/qt5ct/colors", "/usr/local/share/qt5ct/colors", "/usr/share/qt5ct/colors")
[New Thread 0x7fffea81e700 (LWP 2178)]
[New Thread 0x7fffe9f67700 (LWP 2179)]
[New Thread 0x7fffe9766700 (LWP 2180)]

Thread 1 "qt5ct" received signal SIGSEGV, Segmentation fault.
0x00007ffff6bd2d25 in __tzfile_read () from /usr/lib/libc.so.6
(gdb) bt full
#0 0x00007ffff6bd2d25 in __tzfile_read () at /usr/lib/libc.so.6
#1 0x00007ffff6bd2961 in tzset_internal () at /usr/lib/libc.so.6
#2 0x00007ffff6bd2ab1 in tzset () at /usr/lib/libc.so.6
#3 0x00007ffff6bd188d in timelocal () at /usr/lib/libc.so.6
#4 0x00007ffff6f86bdc in () at /usr/lib/libQt5Core.so.5
#5 0x00007ffff6f872a0 in () at /usr/lib/libQt5Core.so.5
#6 0x00007ffff6f873be in () at /usr/lib/libQt5Core.so.5
#7 0x00007ffff6f878dd in () at /usr/lib/libQt5Core.so.5
#8 0x00007ffff6f88e79 in QDateTime::setMSecsSinceEpoch(long long) ()
at /usr/lib/libQt5Core.so.5
#9 0x00007ffff6f8a78d in QDateTime::fromMSecsSinceEpoch(long long, Qt::TimeSpec, int) () at /usr/lib/libQt5Core.so.5
#10 0x00007ffff6f8ae32 in QDateTime::fromMSecsSinceEpoch(long long) ()
at /usr/lib/libQt5Core.so.5
#11 0x00007ffff704126f in QFileInfo::fileTime(QFileDevice::FileTime) const ()
at /usr/lib/libQt5Core.so.5
#12 0x00007ffff7041433 in QFileInfo::lastModified() const ()
at /usr/lib/libQt5Core.so.5
#13 0x00007ffff7078edc in () at /usr/lib/libQt5Core.so.5
#14 0x00007ffff7078ff7 in () at /usr/lib/libQt5Core.so.5
#15 0x00007ffff7079130 in () at /usr/lib/libQt5Core.so.5
#16 0x00007ffff70791f0 in QSettings::QSettings(QString const&, QSettings::Format, QObject*) () at /usr/lib/libQt5Core.so.5
--Type <RET> for more, q to quit, c to continue without paging--c
#17 0x0000555555575d77 in ()
#18 0x0000555555576f79 in ()
#19 0x0000555555576f79 in ()
#20 0x0000555555576f79 in ()
............
............
#23833 0x0000555555578bf4 in ()
#23834 0x00005555555790ec in ()
#23835 0x000055555556690e in ()
#23836 0x00005555555654e3 in ()
#23837 0x00007ffff6b3e223 in __libc_start_main () at /usr/lib/libc.so.6
#23838 0x000055555556567e in ()

The RTC clock is set to local not UTC.

And does setting it to UTC fix it?

From timedatectl:

Warning: The system is configured to read the RTC time in the local time zone.
This mode cannot be fully supported. It will create various problems
with time zone changes and daylight saving time adjustments. The RTC
time is never updated, it relies on external facilities to maintain it.
If at all possible, use RTC in UTC by calling
'timedatectl set-local-rtc 0'.

It's still there with RTC set to UTC. I also tried a workaround with libfaketime but it doesn't help.

check the date of .config/qt5ct/qt5ct.conf, it's probably set to somewhere in the future

No it's not that. I Uninstalled the package, deleted the ~/.config/qt5ct folder and reinstalled it but it's not fixed.

What's the output of 'ls -l /etc/localtime' and 'timedatectl'?

ls -l /etc/localtime
lrwxrwxrwx 1 root root 35 окт 1 2016 /etc/localtime -> ../usr/share/zoneinfo/Europe/Skopje

timedatectl
Local time: пет 2018-12-07 17:11:38 CET
Universal time: пет 2018-12-07 16:11:38 UTC
RTC time: пет 2018-12-07 16:11:38
Time zone: Europe/Skopje (CET, +0100)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no

No idea where the problem is then. You'll need to recompile glibc with debug symbols to find out exactly where in __tzfile_read it's crashing.

PS: Please stop refreshing the page, you keep posting the same comment over and over.