Formula: minute hour day-of-month month day-of-week
Cron expressions define recurring schedules using 5 fields: minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–6, where 0 is Sunday). Special characters: * (every), */N (every Nth), N-M (range), N,M (list). For example, '0 9 * * 1-5' means 'at 9:00 AM, Monday through Friday'. Cron is used in Unix/Linux, CI/CD pipelines, and cloud schedulers.