What is a cron expression?
A cron expression schedules tasks on Linux servers, CI pipelines and cloud functions. It has five fields separated by spaces:
- minute (0–59)
- hour (0–23)
- day of month (1–31)
- month (1–12, or JAN–DEC)
- weekday (0–7, or SUN–SAT; both 0 and 7 mean Sunday)
Supported syntax
*– every value (e.g.*in the hour field = every hour)*/n– every n units (e.g.*/15= every 15 minutes)a-b– a range (e.g.9-17= 9am through 5pm)a,b,c– a list (e.g.1,15,30= minutes 1, 15 and 30)a-b/n– step inside a range (e.g.0-30/10= 0, 10, 20, 30)
Common examples
0 2 * * *– run at 2:00 AM every day (classic nightly backup)*/5 * * * *– run every 5 minutes (monitoring)30 9 * * 1-5– run at 9:30 AM on weekdays (morning report)0 0 1 * *– run at midnight on the first of every month (billing)0 22 * * 6,0– run at 10 PM on Saturday and Sunday
If both the day-of-month and weekday fields are restricted (non-*), cron runs when either matches — this OR behavior confuses many developers, so test your schedule with this parser before deploying.