A script to save the current time during shutdown/reboot and then restore it upon power-up. This can be useful for machines which lack a battery-backed real time clock, so that we still ensure time never goes backwards.
It is strongly advised that you also run an NTP client to set the correct time once the network is up.
For Debian and derivatives:
dpkg-buildpackage -uc -us
Then find the built package one level up in the directory hierarchy.