Comment # 18 on bug 1148824 from Jan Zerebecki

If you can, I'd prefer the

%source_date_epoch_from_changelog 1

to be in something like a

"%if "%_project" == "openSUSE:Factory"

so that it is only enabled in Factory and its stagings and similar, but not in
projects that simply use Factory like devel projects.

This setting is only used in OBS to trigger an error if there is no date
available. I will come up with a solution that doesn't need a conditional in
prjconf. But for now this might be an easy way to not surprise people who build
packages without a changelog that are not intended to be submitted to Factory.
See: https://bugzilla.suse.com/show_bug.cgi?id=1220540#c6