If you want to run a job in the future but don't want to use cron because the command should only run once, you can do it with the at service. For example, if you want to run myjob at 10:30 PM, enter this command:
at 22:30 myjob
End the input with a CONTROL-D (at reads the commands from the standard input).
To check that the job has been scheduled, use atq, or to remove it, use atrm. You also can schedule jobs days into the future by adding the date (in DD.MM.YY format; for example, at 22:30 30.09.03).
There isn't too much else to the at command. at actually does not see much use in common practice. However, it can be handy for the odd time that you need to shut the system down in the future.