To learn more about configuring automated tasks, refer to the following resources.
cron man page — overview of cron.
crontab man pages in sections 1 and 5 — The man page in section 1 contains an overview of the crontab file. The man page in section 5 contains the format for the file and some example entries.
/usr/share/doc/at-<version>/timespec contains more detailed information about the times that can be specified for cron jobs.
anacron man page — description of anacron and its command line options.
anacrontab man page — brief overview of the anacron configuration file.
/usr/share/doc/anacron-<version>/README — describes Anacron and why it is useful.
at man page — description of at and batch and their command line options.