Cron implementations differ. This tool uses standard five-field Unix syntax and UTC, with the traditional OR rule when both day-of-month and day-of-week are restricted. It does not support Quartz seconds, years, ?, L, W or #.
How to use this cron expression calculator
- Enter a portable five-field Unix cron expression or choose a preset.
- Choose the UTC time from which the preview should begin.
- Validate the syntax, read the explanation and inspect the next five runs.
Validate a five-field Unix cron expression
A portable crontab schedule has five space-separated fields in this order: minute, hour, day of month, month and day of week. This calculator accepts wildcards, comma-separated lists, numeric ranges and step values. Month names from JAN to DEC and weekday names from SUN to SAT are also accepted. It rejects Quartz-only seconds, years and operators so an unsupported expression cannot look valid by accident.
| Field | Allowed values | Example |
|---|---|---|
| Minute | 0–59 | */15 |
| Hour | 0–23 | 9-17 |
| Day of month | 1–31 | 1,15 |
| Month | 1–12 or JAN–DEC | JAN,JUL |
| Day of week | 0–7 or SUN–SAT | 1-5 |
Preview the next five cron runs in UTC
The preview starts after the selected UTC minute and walks forward until it finds five matching executions. Showing concrete ISO 8601 timestamps catches mistakes that a sentence can hide. For example, */15 9-17 * * 1-5 runs every 15 minutes from 09:00 through 17:45 UTC on Monday through Friday.
Day-of-month and day-of-week use an OR rule
Traditional Unix cron treats the two day fields specially. When either field is unrestricted, the restricted field controls the date. When both are restricted, a run occurs when either one matches. Therefore 0 9 1 * MON runs at 09:00 UTC on every first day of the month and every Monday. This differs from a simple five-way AND test and is covered by automated examples.
Portable Unix cron versus Quartz and hosted schedulers
Quartz commonly adds a seconds field and supports operators such as ?, L, W and #. Cloud schedulers can add a year field, require a timezone setting or change day-field rules. Code Compass does not guess which dialect you meant. Verify the generated schedule against the documentation for the exact daemon, framework or hosting platform that will execute it.
Privacy and preview limits
Parsing and calculation run in the current browser tab, and the expression is not submitted to Code Compass. Upcoming times are displayed in UTC so browser locale and daylight-saving transitions cannot silently change the preview. A real server can run in another timezone. The search is bounded to roughly 25 years and may reject an exceptionally sparse schedule rather than claim an incomplete answer.
Related developer tools
Use the Unix Timestamp Converter to inspect an epoch value, the JSON Formatter for scheduler configuration, or the HTTP Status Code Lookup when debugging the endpoint a scheduled job calls.
Frequently asked questions
Does this calculator support Quartz cron?
No. It supports the five-field Unix format and rejects Quartz-only fields and operators.
Which timezone does the preview use?
The calculation and displayed ISO timestamps use UTC. Check the timezone configured on the real scheduler.
Can 0 and 7 both mean Sunday?
Yes. Either numeric value is normalized to Sunday in the day-of-week field.