nightly.sh: Get the relative date from the Rawhide data
nightly.sh: Get the relative date from the Rawhide data

Signed-off-by: Stephen Gallagher <ff239cad7a3e5aa2b398edf92aa8c4be6690609b@redhat.com>

fedora-modularity/baseruntime-package-lists,sgallagher/baseruntime-package-lists,fedora-modularity/baseruntime-package-lists,sgallagher/baseruntime-package-lists,fedora-modularity/baseruntime-package-lists,sgallagher/baseruntime-package-lists