The 'at' command basically executes a command at a specified time, surprisingly useful if you need to print something in a certain time slot and you're useless at remembering stuff..
The Below command will run the jobtodo script at 15:00:
at -m 15:00 < jobtodo.sh
To list all jobs scheduled run this:
to remove jobs (job 3 for example):
To be honest if you want something that will run every day your better off looking at crontab. But if you after something quick and simple this will do just nicely. I use this command at work for running scripts at set times of the day, that way I wont forget.