Cron Expression Explainer

Translate complex crontab schedule expressions into plain English. Preview next upcoming execution timestamps, inspect field syntax, and test cron schedules.

Cron Expression

Plain English Translation

Runs at 9:00 AM, on every weekday (Mon–Fri).

Next 8 Scheduled Executions

Run #1Thu, Aug 20, 2026, 09:00 AM
Run #2Fri, Aug 21, 2026, 09:00 AM
Run #3Mon, Aug 24, 2026, 09:00 AM
Run #4Tue, Aug 25, 2026, 09:00 AM
Run #5Wed, Aug 26, 2026, 09:00 AM

Quick Answer: How to Read a 5-Field Crontab Expression

Standard crontab expressions follow the syntax [minute] [hour] [day_of_month] [month] [day_of_week]. An expression like 0 9 * * 1-5 means At 9:00 AM, Monday through Friday. An asterisk (*) matches all values, , specifies value lists (e.g. 1,15), - specifies ranges (e.g. 1-5), and / specifies step intervals (e.g. */15).

Crontab 5-Field Anatomy

Field 1Minute0 – 59
Field 2Hour0 – 23
Field 3Day of Month1 – 31
Field 4Month1 – 12 (Jan–Dec)
Field 5Day of Week0 – 6 (Sun–Sat)

Crontab Special Characters Reference

SymbolMeaningExampleDescription
*Any / Every value* * * * *Triggers every minute of every hour
/Step / Interval values*/15 * * * *Every 15 minutes (at :00, :15, :30, :45)
,Value list separator0 0 1,15 * *At midnight on the 1st and 15th of the month
-Range of values0 9-17 * * 1-5Every hour between 9 AM and 5 PM on weekdays

Step-by-Step Case Study: Enterprise Automation Schedules

Here is how you write production cron expressions for common backend cron tasks:

  1. Nightly Database Backup: 0 2 * * * (Runs daily at 2:00 AM when server traffic is lowest).
  2. Bi-Weekly Payroll Processing: 0 6 1,15 * * (Runs at 6:00 AM on the 1st and 15th of every month).
  3. Weekly Sunday Maintenance Window: 30 3 * * 0 (Runs at 3:30 AM every Sunday morning).
  4. Hourly Health Check API Ping: 0 * * * * (Runs at the top of every hour).

Frequently Asked Questions

What are the 5 fields of a standard Unix crontab expression?
A standard Unix/Linux crontab contains 5 whitespace-separated fields: 1. Minute (0–59), 2. Hour (0–23), 3. Day of Month (1–31), 4. Month (1–12 or JAN–DEC), and 5. Day of Week (0–6 or SUN–SAT, where 0 and 7 both represent Sunday).
What does */5 or */15 mean in a cron expression?
The forward slash (/) defines step/interval values. When placed after an asterisk (*/N) or range, it specifies repetitions. For example, '*/5 * * * *' in the minute field means 'every 5 minutes'. '0 */3 * * *' in the hour field means 'every 3 hours on the hour'.
How does cron handle both Day of Month and Day of Week together?
In standard POSIX crontab engines, if both Day of Month (DOM) and Day of Week (DOW) are specified with non-asterisk values (e.g., '0 0 15 * 1'), cron evaluates them as an OR (union) condition. The command will trigger if EITHER the 15th of the month arrives OR if it is Monday.
What are cron shorthand macros like @daily, @hourly, and @reboot?
Many modern cron daemons (like Vixie cron and systemd) support shorthand aliases: '@hourly' (0 * * * *), '@daily' or '@midnight' (0 0 * * *), '@weekly' (0 0 * * 0), '@monthly' (0 0 1 * *), '@yearly' (0 0 1 1 *), and '@reboot' (runs once upon server startup).
How do timezone differences affect cron jobs in GitHub Actions and AWS?
Cloud services like GitHub Actions, AWS EventBridge, and Vercel Cron execute all cron schedules in UTC (Coordinated Universal Time). If you want a job to trigger at 9:00 AM Eastern Time (UTC-5), you must configure your cron expression for 14:00 UTC ('0 14 * * *').
What is the difference between 5-field and 6-field cron expressions?
Standard Linux crontab uses 5 fields (Minute to Weekday). However, frameworks like Quartz, Spring Boot, and AWS EventBridge often support a 6-field or 7-field format that includes Seconds (at the beginning) or Year (at the end).
How do I redirect cron job output and errors to a log file?
In Linux crontab, append '>> /var/log/myjob.log 2>&1' to capture both standard output (stdout) and standard error (stderr) into a persistent log file (e.g. '0 2 * * * /usr/bin/python3 /app/backup.py >> /var/log/backup.log 2>&1').

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