Cron Expression Explainer
Translate cron expressions into plain English, see the next 5 scheduled run times, and explore common examples. All client-side.
| Expression | Description |
|---|
| Field | Allowed Values | Allowed Special Chars |
|---|---|---|
| Minute | 0–59 | * , - / |
| Hour | 0–23 | * , - / |
| Day of Month | 1–31 | * , - / ? |
| Month | 1–12 | * , - / |
| Day of Week | 0–6 (Sun=0) | * , - / |
Frequently Asked Questions
* means "every". For example, 0 0 * * * means "at midnight every day" and */15 * * * * means "every 15 minutes".*/5 in the minute field means "every 5 minutes". 0/15 means "starting at 0, every 15 units". Steps are especially useful for scheduling tasks at regular intervals without listing every value.0–59), Hour (0–23), Day of month (1–31), Month (1–12 or JAN–DEC), Day of week (0–7 where both 0 and 7 represent Sunday, or SUN–SAT). Special characters: * = every value; , = list (e.g., 1,3,5); - = range (e.g., 1-5); / = step (e.g., */15). Some cron implementations add a 6th seconds field or a 7th year field, but the standard POSIX cron uses five fields.@reboot — runs once at startup; @yearly or @annually — runs January 1st at midnight (0 0 1 1 *); @monthly — runs the 1st of each month at midnight (0 0 1 * *); @weekly — runs Sunday at midnight (0 0 * * 0); @daily or @midnight — runs every day at midnight (0 0 * * *); @hourly — runs at the start of each hour (0 * * * *). These are supported by Vixie cron (the most common implementation on Linux), but check your system's cron documentation to confirm./etc/timezone or /etc/localtime. If your server is in UTC and you want a job to run at 9am New York time, you must calculate the UTC offset (e.g., 14:00 UTC in winter, 13:00 UTC in summer). Some cron implementations (Vixie cron, systemd timers) support a TZ= environment variable per crontab to override the timezone. Best practice: keep servers in UTC and document any timezone conversions explicitly in comments alongside the cron expression.crontab -e manages a per-user crontab — jobs run as the current user. /etc/cron.d/ holds system-wide crontab files — each file can specify a user column (6th field) to run jobs as a specific user. /etc/cron.daily/, /etc/cron.hourly/, /etc/cron.weekly/, and /etc/cron.monthly/ contain shell scripts (not cron expressions) that run-parts executes at predefined intervals managed by the system cron. For application-level scheduled tasks, /etc/cron.d/ with an explicit username is the cleanest approach.grep CRON /var/log/syslog (Debian/Ubuntu) or journalctl -u cron (systemd). 2. Redirect output — add 2>&1 >> /tmp/cron.log to your cron command to capture stdout and stderr. 3. Check environment — cron runs with a minimal PATH; use full paths for commands (/usr/bin/php not php). 4. Check permissions — the cron script must be executable and readable by the cron user. 5. Verify the expression — use this tool to confirm the schedule is what you expect. 6. Test manually — run the command directly as the cron user with sudo -u username command.* * * * * php artisan schedule:run) with all logic in code.*/5 * * * * /path/to/command. The */5 in the minute field means "every value divisible by 5" — i.e., at minutes 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55. Other common intervals: every 10 minutes: */10 * * * *; every 15 minutes: */15 * * * *; every 30 minutes: */30 * * * * (or 0,30 * * * *); every 2 hours: 0 */2 * * *; every weekday at 9am: 0 9 * * 1-5. Note: */5 is not exactly "every 5 minutes from now" — it triggers at fixed intervals aligned to the clock (0, 5, 10…).About This Cron Explainer
This free cron explainer parses any cron expression and describes it in plain English, showing the next 5 scheduled run times. Enter a 5-field or 6-field cron expression (with seconds) to see exactly when it will execute.
Cron expressions can be difficult to read and write correctly. A single misplaced asterisk or comma can change a job from running every minute to running once a month. This tool helps you verify a schedule before deploying it to production.
When to use this tool
- Verifying a cron schedule before deploying to production
- Debugging why a scheduled job ran at unexpected times
- Learning cron syntax interactively with real examples
- Generating expressions for common intervals (hourly, daily, weekly)
Standards & References
How the Cron Explainer Works
Cron expressions describe a schedule in five space-separated fields. This tool parses, explains, and simulates them entirely in the browser.
Parse Each Field
Each of the 5 fields (minute, hour, day-of-month, month, day-of-week) is parsed with full support for * (all), - (range), / (step), and , (list) operators to expand into a set of matching values.
Build Human Sentence
The expanded field values are assembled into a plain English sentence. Single values become specific names (e.g., "Monday", "January"). Multiple values use lists or ranges for readability.
Simulate Next 5 Runs
The tool steps through time minute-by-minute from now, checking all 5 fields simultaneously, until it finds 5 matching moments. Results are displayed in UTC to match how cron daemons typically run.
Common Use Cases
Scheduled Backups
Verify that your backup cron runs at the right time — typically off-peak hours in the server's timezone. Use 0 2 * * * for daily at 2 AM and confirm it doesn't conflict with other scheduled tasks.
Automated Report Generation
Schedule weekly or monthly reports with expressions like 0 8 * * 1 (every Monday at 8 AM) or 0 9 1 * * (first of every month at 9 AM). See the plain-English description before deploying.
Database Cleanup Jobs
Purge expired sessions, soft-deleted records, or old log entries with a nightly job. Test complex expressions like 30 3 * * 0 (Sunday at 3:30 AM) to ensure cleanup runs at the intended low-traffic window.
Monitoring Heartbeats
Health-check pings to uptime monitors run every 1–5 minutes (*/5 * * * *). Verify the interval is correct and see the next 5 check times to ensure no gaps from a misconfigured expression.
Cache Warmup & CDN Invalidation
Pre-warm caches before business hours to ensure fast first-page loads. Schedule 0 7 * * 1-5 (weekdays at 7 AM) and confirm the warmup completes before peak traffic using the next-run simulation.
Digest & Newsletter Emails
Weekly newsletters, daily digests, and subscription summaries need precise scheduling. Use the explainer to confirm expressions like 0 10 * * 2 (Tuesday at 10 AM) send at the right day and time globally.
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