Cron Expression Parser

Field	Value	Range	Meaning
Minute	0	0–59	0
Hour	9	0–23	9
Day (month)	*	1–31	every day
Month	*	1–12	every month
Day (week)	1-5	0–6	1-5 (range)

Field

Value

Range

Meaning

Minute

0–59

Hour

0–23

Day (month)

1–31

every day

Month

1–12

every month

Day (week)

1-5

0–6

1-5 (range)

Understanding cron syntax

Cron is the backbone of scheduled automation on Unix-like systems. A cron expression lets you specify a schedule as precise as “every weekday at 8:05 AM” or as broad as “once a year on January 1st.” Once you understand the five-field structure, you can express virtually any recurring schedule.

Field reference

Minute: 0–59 — use */5 for every 5 minutes
Hour: 0–23 — use 9-17 for business hours
Day of month: 1–31 — use 1,15 for twice a month
Month: 1–12 or JAN–DEC — use */3 for quarterly
Day of week: 0–6 (Sun=0) or SUN–SAT — use 1-5 for weekdays

Common patterns

* * * * * — every minute
0 * * * * — top of every hour
0 0 * * * — daily at midnight
0 0 * * 0 — every Sunday at midnight
0 0 1 * * — first of every month at midnight
0 0 1 1 * — once a year on January 1st
*/15 * * * * — every 15 minutes
0 9-17 * * 1-5 — every hour during business hours on weekdays

Common use cases

Developers paste inherited cron jobs from a legacy codebase here to understand what schedule they actually run on before modifying them. SREs use the next-run preview to verify that a maintenance window job won't fire during peak traffic hours. Engineers debugging missed scheduled tasks use the parser to confirm the expression is syntactically valid and that the next execution time aligns with their expectations. Teams reviewing GitHub Actions workflow files paste the schedule trigger to translate it into plain English for non-technical stakeholders.

Cron in cloud schedulers and CI/CD

Modern infrastructure uses cron syntax far beyond traditional Unix crontab. GitHub Actions uses cron expressions in the scheduletrigger — all times are in UTC, and the minimum interval is every 5 minutes. AWS EventBridge (CloudWatch Events) supports cron expressions with a 6-field format that adds a year field. GCP Cloud Scheduler uses standard 5-field cron in the user's configured timezone. Kubernetes CronJobs use the same 5-field syntax. Always check which scheduler you are targeting, since the year field and timezone handling differ between platforms.

Frequently asked questions

What is a cron expression?

A cron expression is a string of five (or six) fields separated by spaces that defines a recurring schedule for automated tasks. It is used in Unix-like systems, CI/CD pipelines, cloud schedulers (AWS EventBridge, GCP Cloud Scheduler), and application frameworks to trigger jobs at specific times.

What are the five fields in a cron expression?

The five fields are, in order: Minute (0–59), Hour (0–23), Day of Month (1–31), Month (1–12 or JAN–DEC), and Day of Week (0–6 or SUN–SAT, where 0 = Sunday). Example: '0 9 * * 1-5' means 9:00 AM every weekday.

What does */15 mean in a cron expression?

The */n syntax means 'every n units'. So */15 in the minute field means 'every 15 minutes' (i.e., at :00, :15, :30, :45). Similarly, */2 in the hour field means 'every 2 hours'.

Can I use comm ranges together?

Yes. You can combine lists (1,3,5), ranges (1-5), and steps (*/2 or 1-10/2) in a single field using commas. For example, '0,30 9-17 * * 1-5' means every 30 minutes from 9 AM to 5 PM on weekdays.

Why do some cron expressions have 6 or 7 fields?

The standard Unix cron uses 5 fields. Some systems add a seconds field at the start (making it 6 fields), or a year field at the end (making it 7 fields). This parser handles the standard 5-field format used by most Linux crons, GitHub Actions schedules, and cloud schedulers.