This is an interactive cron expression reference and decoder. Type a cron string and it explains, in plain English, when the job will run. It supports the three dialects you meet in practice: standard five-field Unix cron, Quartz (with a seconds field), and AWS EventBridge — and lists every field’s range and the special characters each accepts.
Three cron dialects explained
Standard Unix cron uses five fields: minute hour day-of-month month day-of-week. This is what you write in a system crontab, in most CI tools, and in Kubernetes CronJob specs. Day-of-week uses 0 for Sunday (some implementations also accept 7 for Sunday).
Quartz cron (used by Java schedulers, Spring, and Jenkins) prepends a mandatory seconds field and appends an optional year field, giving six or seven fields total: second minute hour day-of-month month day-of-week [year]. The extra second field means Quartz can fire sub-minute — down to once per second — which standard cron cannot do.
AWS EventBridge uses six required fields: minute hour day-of-month month day-of-week year. It requires a ? in exactly one of the day-of-month or day-of-week fields when the other is specified, resolving the “either-or” ambiguity of standard cron explicitly.
Special characters — field by field
| Character | Meaning | Example |
|---|---|---|
* | Every value | * * * * * fires every minute |
, | List | 0,30 in minute = minute 0 and 30 |
- | Range | 9-17 in hour = 09:00 to 17:00 |
/ | Step | */15 in minute = every 15 minutes |
? | No specific value (Quartz/AWS) | Use in day-of-month or day-of-week when the other is set |
L | Last (Quartz) | L in day-of-month = last day of month |
W | Nearest weekday (Quartz) | 15W = nearest weekday to the 15th |
# | Nth weekday (Quartz) | 6#3 = third Friday of the month |
How the decoder works
The decoder splits your expression on whitespace, counts the fields to identify the format, validates each field against its allowed range, and translates field by field into English. For example 0 9 * * 1-5 becomes “at minute 0, hour 9, on Monday through Friday.” Fields with steps are expanded into their word form (“every 15 minutes”), and named weekdays replace numeric codes.
Practical notes for each platform
When deploying to Kubernetes, the day-of-week range in standard cron matters: 1-5 means Monday to Friday because week days are numbered 1 (Mon) through 7 (Sun) in ISO 8601, but in cron 0 or 7 both mean Sunday. Check your scheduler documentation for which convention applies.
For AWS EventBridge, the expression always lives inside cron(...), for example cron(0 9 * * ? *) for daily at 09:00 UTC. The ? in day-of-week is required when day-of-month is a wildcard and vice versa.
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