Cron Schedule Syntax: The Complete Developer Reference

What Is a Cron Schedule?

A cron schedule is a compact string of fields telling a scheduler exactly when to run a job — minute, hour, day, month, weekday. It's the timing rule, not the execution: it just tells a cron daemon, CI runner, or cloud scheduler "wake up now." For broader background on what cron is and how the daemon processes these strings, see our plain-English guide to cron.

Once you can read a cron schedule at a glance, you can write one for almost any recurring task — backups, health checks, report generation — without guessing.

The 5 Fields of a Cron Schedule (With a Diagram)

Standard cron schedule format uses five fields, each separated by a space, in this fixed order:

*    *    *    *    *
-    -    -    -    -
|    |    |    |    |
|    |    |    |    +----- day of week (0-6, Sun=0)
|    |    |    +---------- month (1-12)
|    |    +--------------- day of month (1-31)
|    +-------------------- hour (0-23)
+------------------------- minute (0-59)

So minute hour day month weekday, always in that order. A schedule of 30 14 * * * means minute 30, hour 14 — 2:30 PM every day, since day-of-month, month, and day-of-week are all wildcards. Memorizing this field order is the single biggest unlock for reading or writing any cron expression correctly, whether in a crontab, a GitHub Actions workflow, or an AWS EventBridge rule.

Special Characters: *, ,, -, / (and When to Use Them)

Cron schedule syntax relies on four special characters to express ranges and repetition without listing every value:

• * (asterisk) — matches every possible value for that field. * * * * * runs every minute of every day.
• , (comma) — separates a list of specific values. 0 9,17 * * * runs at 9:00 AM and 5:00 PM.
• - (hyphen) — defines an inclusive range. 0 9-17 * * * runs at the top of every hour from 9 AM through 5 PM.
• / (slash) — defines a step value, usually paired with a range or wildcard. */5 * * * * runs every 5 minutes; 0 */2 * * * runs every 2 hours.

These can be combined: 0,30 9-17 * * 1-5 runs at :00 and :30 past every hour from 9 AM to 5 PM, Monday through Friday.

Shortcuts: @daily, @hourly, @weekly, and More

Many cron implementations support nickname shortcuts that expand to standard five-field equivalents:

Shortcut	Equivalent	Runs
@yearly / @annually	0 0 1 1 *	Once a year, Jan 1 at midnight
@monthly	0 0 1 * *	Once a month, on the 1st at midnight
@weekly	0 0 * * 0	Once a week, Sunday at midnight
@daily / @midnight	0 0 * * *	Once a day at midnight
@hourly	0 * * * *	Once an hour, at minute 0

Support isn't universal. Vixie cron (the standard Linux/Unix cron) accepts these shortcuts, while some managed platforms and the Quartz scheduler used in many Java frameworks do not, requiring full five- or six-field syntax instead. Always check your target platform's docs before relying on a shortcut.

Common Cron Schedule Examples (Copy-Paste Table)

Here are the cron schedule examples developers search for most, ready to paste:

Schedule	Cron Expression	Meaning
Every minute	* * * * *	Runs every minute
Every 5 minutes	*/5 * * * *	Runs on the 5-minute mark
Every hour	0 * * * *	Runs at the top of every hour
Every day at midnight	0 0 * * *	Cron schedule for every day, run once
Every day at 9 AM	0 9 * * *	Daily, 9:00 AM
Weekdays at 9 AM	0 9 * * 1-5	Monday–Friday only
Every Sunday at midnight	0 0 * * 0	Weekly, start of week
First of every month	0 0 1 * *	Monthly, 1st day
Every 15 minutes	*/15 * * * *	Four times per hour
Twice daily	0 6,18 * * *	6 AM and 6 PM

Bookmark this table for the schedules you'll reuse across projects — it covers the vast majority of real-world scheduling needs without deriving anything from scratch.

5 Mistakes That Break a Cron Schedule

1. Day-of-month AND day-of-week logic. If both fields are restricted (not *), most cron implementations treat them as OR, not AND. 0 9 15 * 5 runs on the 15th and every Friday — not just when the 15th falls on a Friday. This trips up far more people than the syntax itself.

2. Is Sunday 0 or 7? Both, depending on implementation — standard cron accepts 0 and 7 as Sunday for compatibility, but not every parser agrees. When portability matters, use 0 and test explicitly.

3. Ignoring cron timezone. A cron schedule fires according to the system clock it runs on — often UTC on servers and cloud schedulers like AWS EventBridge or Kubernetes CronJob, but local time in a default Linux crontab. "9 AM" can mean very different moments depending on where the scheduler runs.

4. Assuming extended syntax is portable. Characters like L (last day), W (nearest weekday), and # (nth weekday of month) work in Quartz scheduler but aren't part of standard Vixie cron — dropping them into a Linux crontab or GitHub Actions schedule will either error out or silently misbehave.

5. Leaving a field blank instead of using *. Cron requires exactly five fields; an empty or missing field breaks parsing entirely rather than defaulting to "any value."

A Valid Schedule Doesn't Mean the Job Ran

Everything above governs when cron attempts a job — it says nothing about whether that job succeeded. A cron schedule with perfect syntax will still fire on a server that's down, trigger a script that throws an unhandled exception, or kick off a request that times out silently. Cron itself rarely tells you any of this happened; it just tries again next cycle.

That gap — between "scheduled" and "succeeded" — is where cron job monitoring earns its keep. Our framework for reliable cron jobs walks through tracking execution history, catching failures, and alerting on missed runs. If you want to see how that works for schedules like the ones above, cronevra tracks execution history and alerts you the moment a run fails or never checks in — for any cron schedule you're already running.

Frequently Asked Questions

What does 0 0 * * * mean in a cron schedule?

It means "run at minute 0, hour 0, every day, every month, every day of the week" — once daily at midnight. It's the five-field equivalent of the @daily shortcut and one of the most common cron schedule examples in production use.

How do I schedule a cron job to run every 5 minutes?

Use */5 * * * *, which applies a step value of 5 to the minute field while leaving every other field as a wildcard. This fires at :00, :05, :10, and so on through every hour of every day.

Is Sunday 0 or 7 in a cron schedule?

Standard cron accepts both 0 and 7 as valid representations of Sunday in the day-of-week field, for compatibility with different conventions. Not every scheduler honors 7, though, so use 0 for the most portable, unambiguous result.

Can I use a cron schedule with seconds?

Not in standard five-field Vixie cron, which has no seconds field — its shortest interval is one minute. Some systems, including the Quartz scheduler, use a six-field format with seconds as the first field, so second-level scheduling depends entirely on your platform.

What's the difference between a cron schedule and a crontab file?

A cron schedule is a single line — the five-field expression plus the command — while a crontab file is the full file containing one or more of those scheduled entries for a user or system. Every line in a crontab is technically its own cron schedule.

How do I test if my cron schedule syntax is correct?

Paste the expression into a parser like crontab.guru, which translates it into plain English and flags invalid fields instantly. It's the fastest way to confirm a schedule actually means what you intended before deploying it.