How can I make my computer wake up at a specified time?
Use the rtcwake command, like this:
rtcwake -m no -l -t `date +%s -d 'tomorrow 7:30'`
This is different than using cron. Because after you issue
this command you can shutdown your computer and it will
wake up at the time you want. Pretty cool.
Here's a breakdown of the rtcwake options:
-m no = don't shutdown now
-l = Use local time
-t <time_t> = This option wants the seconds since 1970.
Which you can make with the date command in backticks.