Comment # 11 on bug 1223169 from Bernhard Wiedemann

Found the correct reproducer now:
osc build --noservice --vm-type=kvm \
 --build-opt=--vm-custom-opt=-rtc\ base=2038-01-20T00:00:00 standard x86_64

while a 2037 build worked fine, so (surpisingly) it is a year-2038 issue.