Cron Expression Explainer — Parse Cron in Plain English

Cron Expression Format

A standard cron expression has 5 space-separated fields. Some platforms (AWS EventBridge, Spring, Quartz) extend this to 6 fields by adding a seconds field at the start.

Field	Range	Special chars	Example
Minute	0–59	`* , - /`	`30` = at :30
Hour	0–23	`* , - /`	`9` = 9am
Day of month	1–31	`* , - / ?`	`1` = 1st of month
Month	1–12 or JAN–DEC	`* , - /`	`3` = March
Day of week	0–7 or SUN–SAT (0=7=Sunday)	`* , - /`	`1-5` = weekdays

Special character meanings

Char	Meaning	Example
`*`	Every value in the field	`* * * * *` — every minute
`,`	List of values	`1,15,30` — at minutes 1, 15, and 30
`-`	Range of values	`1-5` — Monday through Friday
`/`	Step values	`*/15` — every 15 units

Common Cron Patterns

Expression	Meaning
`* * * * *`	Every minute
`0 * * * *`	Every hour at :00
`0 0 * * *`	Daily at midnight
`0 9 * * 1-5`	9am on weekdays
`0 0 1 * *`	First day of every month at midnight
`/15 * * *`	Every 15 minutes
`0 0 * * 0`	Every Sunday at midnight
`0 8-18 * * 1-5`	Every hour between 8am–6pm on weekdays
`0 0 1 1 *`	Once a year — January 1st at midnight

Platform differences to watch out for

Linux cron / crontab — Classic 5-field format. Day-of-week 0 and 7 both mean Sunday.
GitHub Actions — Uses standard 5-field cron. All times are UTC. Minimum interval is every 5 minutes.
AWS EventBridge — 6-field format with a year field at the end. Uses ? to indicate "no specific value" for day-of-month or day-of-week (only one can be active at a time).
Kubernetes CronJobs — Standard 5-field. Timezone support added in Kubernetes 1.27 via timeZone field.