Before cron, running a job at 3am meant either staying up or befriending whoever managed the mainframe batch queue — a proposition most Unix programmers found deeply unappealing. Ken Thompson wrote the first cron daemon for Unix V7 in 1979, waking up every minute to check if anything needed running. The crontab syntax that resulted — five cryptic fields of asterisks, numbers, and slashes — has since driven generations of sysadmins to online expression validators, wizards, and quiet moments of despair. The daemon itself, however, has never once missed an appointment.
