Cron Syntax Cheat Sheet

cron job runs a command on a schedule defined by a five-field expression. Each field controls a unit of time — minute, hour, day of month, month, and day of week — and special characters let you express ranges, intervals, lists, and wildcards. This reference covers every field, every character, and the schedules you'll use most.

Rather build than read? Use the Cron Job Generator to construct and preview any expression visually without memorizing the syntax.

The Five Fields

*  *  *  *  *
│  │  │  │  └── Day of week   (0–7, Sun = 0 or 7)
│  │  │  └───── Month         (1–12)
│  │  └──────── Day of month  (1–31)
│  └─────────── Hour          (0–23)
└────────────── Minute        (0–59)

Note: both 0 and 7 mean Sunday in the day-of-week field.

Special Characters

Common Schedules

The expressions you'll reach for most often.

Multi-Value Examples

Combining characters for more precise schedules.

Non-Standard Expressions

Many cron implementations (Quartz, AWS, systemd) support shortcuts and a sixth field. Check your platform's docs.

Shorthand Strings

Supported in most Unix crons and Vixie cron.

Six-Field Cron (Quartz / AWS EventBridge)

Some platforms add a seconds field at the start or a year field at the end.

# Quartz (seconds first)
*  *  *  *  *  *
│  │  │  │  │  └── Year (optional)
│  │  │  │  └───── Day of week
│  │  │  └──────── Month
│  │  └─────────── Day of month
│  └────────────── Hour
└───────────────── Second (0–59)

# AWS EventBridge (rate or cron with year)
cron(0 12 * * ? *)   # Every day at noon UTC
rate(5 minutes)      # Every 5 minutes

Cron Environment

Things that bite developers when running cron jobs in production.

Crontab Commands

Golden Rules

1. Always use absolute paths — cron's PATH is minimal; a command that works in your shell may silently fail in cron.
2. Log your output — append >> /path/to/logfile 2>&1 to every job so failures leave a trace.
3. Test the command first — run the exact command in your shell before scheduling it. If it fails there, it'll fail in cron too.
4. Mind the timezone — production servers usually run UTC. Set TZ= at the top of your crontab if your schedule needs a specific zone.
5. Use @reboot sparingly — it's useful but runs before networking is up, so services that depend on the network may fail.

Tip: Not sure if your expression is right? Paste it into the Cron Job Generator to preview exactly when it will next fire.

Frequently Asked Questions

What are the five fields in a cron expression? From left to right: minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–7, where both 0 and 7 are Sunday).

What does */5 mean in cron? The / is a step character. */5 in the minute field means "every 5 minutes" — it starts at 0 and steps by 5, so it fires at 0, 5, 10, 15, and so on.

How do I run a cron job every day at a specific time? Set the minute and hour fields and use * for the rest. For example, 30 8 * * * runs every day at 8:30 AM.

What is the difference between 0 0 * * 0 and @weekly? They are equivalent. @weekly is a shorthand that expands to 0 0 * * 0 — midnight on Sunday.

Why is my cron job not running? The most common reasons are: the command uses a relative path that isn't in cron's minimal PATH; output isn't redirected so errors are silently discarded; or the timezone doesn't match your expectation. Check logs with grep CRON /var/log/syslog.

Can I run a cron job every second? Not with standard Unix cron, which has a minimum resolution of one minute. For sub-minute scheduling, use a platform that supports a seconds field (like Quartz or AWS EventBridge), or run a loop inside the cron job itself.