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Cron Expression Explainer & Parser

Read cron expressions in plain English + see the next 5 run times. For Linux cron, GitHub Actions, AWS EventBridge, Vercel Cron.

All tools

Cron expression

Explanation

Field breakdown

	Minute
	Hour
	Day of month
	Month
	Day of week

Next run times

Common patterns

Cron expression has 5 fields: minute (0-59) hour (0-23) day (1-31) month (1-12) weekday (0-7, 0=Sun). POSIX standard for Linux cron, GitHub Actions, AWS EventBridge, Vercel Cron.

What is a cron expression?

Cron is the Unix/Linux standard for scheduled tasks — running commands automatically at fixed times. A cron expression has 5 fields:

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

Special characters

* — any value (every).
, — list. E.g. 1,3,5 = at 1, 3, 5.
- — range. E.g. 1-5 = from 1 to 5.
/ — step. E.g. */15 = every 15 units.

When to use cron

Linux server: crontab -e — nightly backups, log rotation.
GitHub Actions: schedule: - cron: '0 9 * * 1-5' — run CI at 9 AM Mon-Fri.
AWS EventBridge / Lambda: trigger functions on a schedule.
Vercel Cron: invoke serverless functions periodically.
Database jobs: PostgreSQL pg_cron, MySQL events.

Common pitfalls

Timezone: Linux cron uses the server's clock (often UTC). Vercel/AWS also UTC. Adjust if you want a specific local time.
Day-of-month vs Day-of-week: when BOTH are not *, POSIX defines it as OR (runs if either matches). The tool handles this correctly.
Sunday = 0 or 7: both are valid in cron.
Step start point: */15 starts from 0 → 0,15,30,45 (not 15,30,45,60).