I'm in panther and I think it worked the same way in Jaguar. I don't know about earlier versions of OS X. But just go to system preferences and then to Energy Saver. Click on Schedule. Set up a time to start up the computer or shut down the computer.
Alternatively, there's a program called Alarm Clock which is distributed with Aladdin Ten for X Utilities volume 1. Alarm Clock is sold individually as shareware which you could register for $7. You could pick it up at any of the following URLs:
http://homepage.mac.com/fahrenba/acse/acse.html
http://allmacintosh.xs4all.nl/preview/225705.html
http://www.versiontracker.com/dyn/moreinfo/mac/12255
http://www.apple.com/downloads/macosx/system_disk_utilities/alarmclockse.html
http://mac.iconet.com.br/preview/225705.html
I did a google search for "Alarm Clock SE" and got a bit carried away, sorry! :-P
Sorry for taking so long to reply to you. I guess I missed your thread ;)