What is a cron expression?

A cron expression is a string of 5 fields (or 6 with seconds) separated by spaces that defines a schedule for recurring tasks. The fields represent, in order: minute, hour, day of month, month, and day of week. For example, '0 9 * * 1' means 'at 9:00 AM every Monday'. Cron is built into Unix/Linux systems and widely used in cloud schedulers, CI/CD pipelines, and server automation.

What do the five fields in a cron expression mean?

The five fields are: (1) Minute — 0–59. (2) Hour — 0–23. (3) Day of month — 1–31. (4) Month — 1–12 or JAN–DEC. (5) Day of week — 0–7 (0 and 7 are both Sunday) or SUN–SAT. An asterisk (*) means 'every'. A comma separates multiple values (1,3,5). A hyphen defines a range (1-5). A slash defines a step (/5 means 'every 5'). Combined: '*/15 9-17 * * 1-5' means 'every 15 minutes, from 9 AM to 5 PM, Monday through Friday'.

What are the common cron presets (@daily, @weekly, etc.)?

@yearly or @annually runs once a year at midnight on January 1 (= '0 0 1 1 *'). @monthly runs once a month at midnight on the 1st (= '0 0 1 * *'). @weekly runs once a week at midnight on Sunday (= '0 0 * * 0'). @daily or @midnight runs once a day at midnight (= '0 0 * * *'). @hourly runs once an hour at the start of the hour (= '0 * * * *'). Not all cron implementations support these shortcuts.

What is the difference between cron and systemd timers?

Traditional cron runs as a daemon and uses crontab files to schedule shell commands. systemd timers are a modern Linux alternative that integrates with systemd — they offer more precise timing, better logging (journalctl), and dependency management. systemd timers can be more complex to set up but provide features cron lacks, like triggering a job shortly after boot if it was missed while the system was off (OnBootSec + Persistent). For most server scheduling needs, cron is simpler and sufficient.

How do I handle timezones in cron?

Standard cron runs in the system's local timezone (set by /etc/localtime or $TZ). This can cause problems during DST transitions — jobs can run twice or not at all. Some cron implementations (like cronie on modern Linux) support CRON_TZ=America/New_York in the crontab. Cloud schedulers (AWS EventBridge, Google Cloud Scheduler, GitHub Actions) typically let you specify a timezone explicitly. For maximum reliability, schedule critical jobs in UTC to avoid DST ambiguity.

Encoding & Conversion

Cron Expression Parser

Parse cron expressions into human-readable schedules — see the next run times instantly.

Cron Expression

Minute

Hour

Day (month)

Month

Day (week)

Description

Every Monday at 09:00

Next 5 Runs

9/21/2026, 9:00:00 AM
9/28/2026, 9:00:00 AM
10/5/2026, 9:00:00 AM
10/12/2026, 9:00:00 AM
10/19/2026, 9:00:00 AM

Common Presets

Cron expressions — frequently asked questions

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