Cron Expression Guide: Syntax, Examples, and Online Parser

Cron expressions control when jobs run in Linux cron, GitHub Actions, Kubernetes CronJobs, AWS EventBridge, and dozens of other schedulers. The syntax is compact but not obvious — 0 9 * * 1-5 takes a moment to read without a reference. An online parser translates expressions to plain English instantly.

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Cron Expression Structure

A standard cron expression has five fields separated by spaces:

┌───────────── minute (0–59)
│ ┌───────────── hour (0–23)
│ │ ┌───────────── day of month (1–31)
│ │ │ ┌───────────── month (1–12)
│ │ │ │ ┌───────────── day of week (0–7, 0 and 7 are Sunday)
│ │ │ │ │
* * * * *

Some systems (Quartz, Spring, AWS Lambda) use a six or seven field format with seconds and/or year. The parser handles both variants.

Special Characters

Character	Meaning	Example
*	Any / every	* * * * * — every minute
,	List	1,15 * * * * — at minute 1 and 15
-	Range	1-5 * * * * — minutes 1 through 5
/	Step	*/15 * * * * — every 15 minutes
L	Last	0 0 L * * — last day of month (non-standard)
#	Nth weekday	0 10 * * 1#2 — 2nd Monday (non-standard)
?	No specific value	Used in day-of-month or day-of-week (Quartz)

20 Common Cron Expressions

Every N minutes

# Every minute
* * * * *

# Every 5 minutes
*/5 * * * *

# Every 15 minutes
*/15 * * * *

# Every 30 minutes
*/30 * * * *

Hourly and daily

# Every hour (top of the hour)
0 * * * *

# Every day at midnight UTC
0 0 * * *

# Every day at 9 AM UTC
0 9 * * *

# Twice a day — 8 AM and 8 PM
0 8,20 * * *

Weekday schedules

# Every weekday at 9 AM
0 9 * * 1-5

# Every Monday at 9 AM
0 9 * * 1

# Monday, Wednesday, Friday at noon
0 12 * * 1,3,5

# Weekends at 10 AM
0 10 * * 0,6

Monthly and quarterly

# First day of every month at midnight
0 0 1 * *

# Last day of every month at 11:59 PM (standard cron)
59 23 28-31 * * (run script that checks if tomorrow is a new month)

# 1st and 15th of every month
0 0 1,15 * *

# First day of each quarter (Jan, Apr, Jul, Oct)
0 0 1 1,4,7,10 *

Specific times

# New Year's Day at midnight
0 0 1 1 *

# Every Sunday at 4 AM (maintenance window)
0 4 * * 0

# Every 6 hours
0 */6 * * *

Platform-Specific Notes

Linux crontab

Standard 5-field syntax. Run crontab -e to edit. Timezone is the system timezone.

# List current crontab
crontab -l

# Edit crontab
crontab -e

GitHub Actions

Uses the 5-field format in UTC. Note that jobs may run up to a few minutes late under load:

on:
  schedule:
    - cron: '0 9 * * 1-5'  # weekdays at 9 AM UTC

AWS EventBridge / CloudWatch Events

Uses a 6-field format with seconds in the first position, or a separate “rate expression”:

cron(0 9 ? * MON-FRI *)
rate(5 minutes)

The ? is required in either day-of-month or day-of-week (not both).

Kubernetes CronJob

Standard 5-field syntax. The timezone field (spec.timeZone) is available in Kubernetes 1.27+:

spec:
  schedule: "0 9 * * 1-5"
  timeZone: "America/New_York"

Reading Cron Expressions at a Glance

Train yourself on these patterns:

• Leading 0 + hour field = “at the top of that hour”
• * in a field = “every unit” of that field
• */n = “every n units”
• Two numbers separated by - = a range
• Numbers separated by , = a list of specific values

So 0 9 * * 1-5 reads: minute 0, hour 9, any day-of-month, any month, weekdays → 9:00 AM every weekday.

Debugging Cron Problems

Job didn’t run? Check:

1. Is the cron daemon running? (systemctl status cron)
2. Is the script executable? (chmod +x script.sh)
3. Does the script use absolute paths? (Cron has a minimal $PATH)
4. Did you save the crontab? (crontab -l to verify)
5. Check logs: /var/log/syslog or /var/log/cron

Output disappeared? Cron sends output to email by default. Redirect to a log file:

0 9 * * * /path/to/script.sh >> /var/log/myjob.log 2>&1

Timezone confusion? Cron runs in the system timezone. For explicit control, set TZ in the crontab:

TZ=America/New_York
0 9 * * 1-5 /path/to/script.sh

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