What actually worked for me:
sudo echo "deb [check-valid-until=no] http://archive.debian.org/debian jessie-backports main" | sudo tee /etc/apt/sources.list.d/backports.list
gpg --keyserver pgpkeys.mit.edu --recv-key 8B48AD6246925553
gpg -a --export 8B48AD6246925553 | sudo apt-key add -
sudo apt-get update
sudo apt-get -t jessie-backports -y install postgresql-9.6
sudo systemctl enable postgresql@9.6-main
Just facing an issue: Error: initdb failed