I've made a small modification to shutdown to allow for an extra time format specifier. It allows specifying hours and minutes away from 'now' in the form +hh:mm. I also added the extra syntax to the relevant manpage. When checking this new relative time, hh is limited to 99999 hours, which corresponds to a little over 11 years.
This syntax allows more easily specifying shutdown times several days in advance, like a preplanned reboot at 1AM on Sunday set up on the previous Friday.
I've attached a patch implementing the changes against the 2.95 release branch.
Thanks,
Will
shutdown-relative-hours.diff