I had a network connection during Upgrade. Still the clock had not been set
correctly (e.g. from NTP).
Also (as opposed to an installation), you can select language and keyboard
layout before upgrading, but you cannot set or confirm the clock settings (e.g.
timezone). Specifically if an Internet connection is available during upgrade,
NTP could be used to set the clock.

After Upgrade I got these messages in first boot:
Mai 30 00:34:18 i7.site /usr/lib/gdm/gdm-x-session[3403]: Fontconfig warning:
Directory/file mtime in the future. New fonts may not be detected.

rpm -qa --last shows the latest installations at:
caribou-gtk3-module-0.4.21-lp151.4.3.x86_64   Do 30 Mai 2019 02:00:50 CEST
caribou-lang-0.4.21-lp151.4.3.noarch          Do 30 Mai 2019 02:00:49 CEST
caribou-gtk-module-common-0.4.21-lp151.4.3.x86_64 Do 30 Mai 2019 02:00:49 CEST

Probably the installation kernel applied timezone correction to an RTC time
that was local time already (Dual boot with Windows 7).

Unfortunately the logs were so long that the initial logs were rotated away
(thanks to more than 2100 texlive packages, or more than 5000 packets to
install or upgrade).