In Linux/Unix systems, AT commands performs specified commands at given times, as long as the commands require no additional input from you. For instance, you may want to print a series of long documents at midnight, so you don't need to tie up the laser printer for hours when other people may need it.
at time at [options] job-ids
Note: The system assigns Job IDs when you use the at command.
-I = Lists current job.
-r = Removes a specified job.
time = Obviously, the time when the commands should run. Unless you specify otherwise (with a.m. or p.m. as a suffix), the system assumes military time.