Build cron schedules visually. Get plain-English explanation, next run times, and copy-ready code for Linux, GitHub Actions, AWS, Kubernetes, Node.js and Python.
0 9 * * 1-5# Edit crontab with: crontab -e 0 9 * * 1-5 /path/to/script.sh
A string of 5 fields (minute, hour, day-of-month, month, day-of-week) that defines when a scheduled task runs. Used by Linux, GitHub Actions, AWS, Kubernetes, and virtually every scheduler.
* is the wildcard — "every valid value". In Minute it means every minute. In Hour it means every hour.
Step notation. */5 in Minute means "every 5th minute" — fires at 0, 5, 10, 15, 20... every hour.
Depends on the platform. Linux uses the server's local timezone. GitHub Actions and AWS EventBridge use UTC.
We generate ready-to-use code for 6 platforms, show the next 8 run times with accurate Indian timezone display, and let you enter a script path for your Linux crontab line.
*Any value*/5Every 5th1-5Range 1 to 51,3,5Specific values0 9 * * 1-5Weekdays 9am*/15 * * * *Every 15 min0 0 1 * *1st of monthA cron expression is a string of text that tells a computer system exactly when to run a scheduled task — automatically, repeatedly, without any human involvement. The name comes from Kronos, the Greek god of time, via the Unix cron daemon (a background process) that has been scheduling tasks on Unix and Linux systems since 1975.
Cron expressions are used by virtually every scheduling system in modern software — Linux servers, GitHub Actions, AWS EventBridge, Kubernetes CronJobs, Apache Airflow, Node.js scheduling libraries, Python schedulers, and hundreds of other tools. Once you understand cron syntax, you can schedule tasks on any of these platforms using the same knowledge.
The standard cron expression consists of exactly five fields separated by spaces:
Each field can contain a specific value, a range, a list, a step value, or the wildcard * meaning "every valid value." The combination of these five fields can express virtually any recurring schedule — from "every minute" to "the last Friday of every third month at 11:59 PM."
The first field controls which minute(s) of the hour the job runs. 0 means the top of the hour. 30 means half past. * means every minute. */15 means every 15 minutes (0, 15, 30, 45).
The second field controls which hour(s) of the day. Uses 24-hour format. 0 is midnight, 9 is 9 AM, 17 is 5 PM, 23 is 11 PM. 9-17 means every hour from 9 AM to 5 PM.
The third field controls which day(s) of the month. 1 is the first of the month, 15 is the 15th, L (in some systems) is the last day. Note: if you set both day-of-month and day-of-week to non-wildcard values, most systems run the job when either condition is true (OR logic), not both.
The fourth field controls which month(s). 1 is January, 12 is December. Some systems also accept three-letter abbreviations: JAN, FEB, MAR, etc.
The fifth field controls which day(s) of the week. 0 and 7 both represent Sunday. 1 is Monday, 5 is Friday, 6 is Saturday. Some systems accept abbreviations: MON, TUE, WED, THU, FRI, SAT, SUN.
| Character | Name | Meaning | Example |
|---|---|---|---|
| * | Asterisk / Wildcard | Every valid value in this field | * * * * * — every minute |
| */n | Step | Every nth value | */5 * * * * — every 5 minutes |
| a-b | Range | Every value from a to b inclusive | 0 9-17 * * * — every hour 9am–5pm |
| a,b,c | List | Specific values only | 0 9,12,17 * * * — 9am, noon, 5pm |
| a-b/n | Range + Step | Every nth value within a range | 0-30/5 * * * * — minutes 0,5,10,15,20,25,30 |
| Expression | Meaning |
|---|---|
| * * * * * | Every minute |
| */2 * * * * | Every 2 minutes |
| */5 * * * * | Every 5 minutes |
| */10 * * * * | Every 10 minutes |
| */15 * * * * | Every 15 minutes |
| */30 * * * * | Every 30 minutes |
| 0 * * * * | Every hour (at :00) |
| 30 * * * * | Every hour at :30 |
| Expression | Meaning |
|---|---|
| 0 0 * * * | Every day at midnight (12:00 AM) |
| 0 6 * * * | Every day at 6:00 AM |
| 0 9 * * * | Every day at 9:00 AM |
| 0 12 * * * | Every day at noon (12:00 PM) |
| 0 17 * * * | Every day at 5:00 PM |
| 0 18 * * * | Every day at 6:00 PM |
| 0 23 * * * | Every day at 11:00 PM |
| 0 0,12 * * * | Every day at midnight and noon |
| 0 8,13,18 * * * | Every day at 8am, 1pm, and 6pm |
| 0 9-17 * * * | Every hour from 9am to 5pm daily |
| Expression | Meaning |
|---|---|
| 0 9 * * 1 | Every Monday at 9:00 AM |
| 0 9 * * 1-5 | Every weekday (Mon–Fri) at 9:00 AM |
| 0 9 * * 1,3,5 | Monday, Wednesday, Friday at 9:00 AM |
| 0 0 * * 0 | Every Sunday at midnight |
| 0 0 * * 6 | Every Saturday at midnight |
| 0 0 * * 6,0 | Every weekend at midnight |
| 0 9 * * 2 | Every Tuesday at 9:00 AM |
| 30 18 * * 5 | Every Friday at 6:30 PM |
| Expression | Meaning |
|---|---|
| 0 0 1 * * | First of every month at midnight |
| 0 0 15 * * | 15th of every month at midnight |
| 0 9 1,15 * * | 1st and 15th of every month at 9am |
| 0 0 1 1 * | January 1st at midnight (New Year) |
| 0 0 1 1,7 * | January 1st and July 1st at midnight |
| 0 9 1 * 1 | First of month, but only if Monday at 9am |
| Expression | Use Case |
|---|---|
| 0 2 * * * | Daily database backup at 2:00 AM (low traffic) |
| */5 * * * * | Check server health every 5 minutes |
| 0 9 * * 1 | Weekly team report every Monday morning |
| 0 0 1 * * | Monthly invoice generation |
| */15 9-17 * * 1-5 | Check API status every 15 min during business hours |
| 0 6 * * * | Daily morning newsletter send |
| 0 0 * * 0 | Weekly database cleanup every Sunday midnight |
| 0 */4 * * * | Refresh cache every 4 hours |
| 30 23 * * * | End-of-day report at 11:30 PM |
| 0 0 1 1 * | Annual data archival on New Year |
| */1 * * * * | Real-time data sync (every minute) |
| 0 9-17/2 * * 1-5 | Every 2 hours during work hours on weekdays |
One of the most common sources of cron confusion is that different platforms use slightly different syntax. The five-field standard cron format works on Linux, but AWS, Kubernetes, and GitHub Actions each have nuances.
The original cron format. Edit with crontab -e. Runs in the server's local timezone. Each line is: expression command.
Uses standard 5-field cron inside a YAML file. Always runs in UTC — if you're in India (IST = UTC+5:30), subtract 5 hours 30 minutes. 0 9 * * * in GitHub Actions runs at 2:30 PM IST.
AWS uses a 6-field format that adds a Year field at the end. Also uses ? instead of * for "no specific value" in day fields. Always UTC.
Uses standard 5-field cron. Timezone support requires Kubernetes 1.25+. The schedule runs in the cluster's timezone by default.
Airflow supports standard 5-field cron plus convenient preset strings: @daily, @hourly, @weekly, @monthly.
The node-cron package supports a 6-field format that adds a Seconds field at the beginning. The standard 5-field cron also works.
Timezone handling is one of the most error-prone aspects of cron scheduling. The same cron expression can produce completely different real-world run times depending on the platform and its timezone configuration.
India Standard Time (IST) is UTC+5:30 — 5 hours and 30 minutes ahead of UTC. To convert a desired IST time to UTC for platforms that require UTC:
| You want to run at (IST) | Use this UTC time | Cron expression |
|---|---|---|
| 6:00 AM IST | 12:30 AM UTC | 30 0 * * * |
| 9:00 AM IST | 3:30 AM UTC | 30 3 * * * |
| 12:00 PM IST (noon) | 6:30 AM UTC | 30 6 * * * |
| 6:00 PM IST | 12:30 PM UTC | 30 12 * * * |
| 9:00 PM IST | 3:30 PM UTC | 30 15 * * * |
| 11:59 PM IST | 6:29 PM UTC | 29 18 * * * |
| 2:00 AM IST | 8:30 PM UTC (previous day) | 30 20 * * * |
GitHub Actions and AWS always run in UTC. 9:00 AM IST is 3:30 AM UTC. Always convert IST to UTC for these platforms.
*/1 technically works but is redundant — every value divisible by 1 is every value. Just use * for clarity.
Standard 5-field cron has minute-level precision. For sub-minute scheduling, use a 6-field implementation (node-cron, Quartz) or trigger from within a running process.
When both day-of-month and day-of-week are non-wildcard, most cron implementations use OR logic: runs when EITHER condition is true. This is counterintuitive.
Always verify the next 5-10 run times before deploying a cron expression. This immediately reveals timezone mistakes, off-by-one errors, and unintended frequencies.
Cron launches a new instance of your job at the scheduled time regardless of whether the previous instance is still running. If your job takes 7 minutes and runs every 5, you'll have overlapping instances.
Three-letter month and day abbreviations (JAN, MON) are supported by Linux cron but not all implementations. Use numbers for maximum compatibility.
Cron expressions are absolute, not relative. */5 in the minute field means "any minute divisible by 5" — always 0,5,10... regardless of when the cron daemon started.
Scheduling on the 31st skips months with fewer than 31 days. For true end-of-month scheduling, most platforms require a script check or the non-standard L operator.
Cron jobs fail silently by default. Always add error handling — either in the script itself or via cron's MAILTO variable — so failures don't go unnoticed.
The cron daemon is a background process that runs continuously on Unix and Linux systems. Every minute, it reads the crontab files (user crontabs at /var/spool/cron/crontabs/ and system crontabs at /etc/cron.d/) and checks whether any scheduled job should run in the current minute. If a job's expression matches the current time, cron launches the job as a new process.
A crontab file contains one job per line. Each line has six components: the five time fields plus the command to execute. Lines beginning with # are comments.
User crontab (crontab -e): Runs jobs as the current user. Jobs defined here are in /var/spool/cron/crontabs/username.
System crontab (/etc/crontab and /etc/cron.d/): Has an additional field for the username to run the job as. Used for system-level tasks.
Most cron implementations support convenient named schedules as alternatives to the 5-field expression:
| Macro | Equivalent | Meaning |
|---|---|---|
| @reboot | (special) | Run once at system startup |
| @yearly / @annually | 0 0 1 1 * | Run once a year |
| @monthly | 0 0 1 * * | Run once a month |
| @weekly | 0 0 * * 0 | Run once a week (Sunday) |
| @daily / @midnight | 0 0 * * * | Run once a day at midnight |
| @hourly | 0 * * * * | Run at the start of every hour |
Cron has a surprisingly long history for a piece of software that most developers take for granted. Understanding its origins explains some of the design decisions that can seem arbitrary today.
The first cron was written by Brian Kernighan (co-creator of C and Unix) at Bell Labs. This version was simple: it woke up once a minute and ran any jobs scheduled for that time. It had a single crontab shared by all users.
Ken Thompson rewrote cron to support per-user crontabs, the design that survives to this day. This version introduced the familiar five-field expression format.
Paul Vixie released a rewrite of cron in 1987 that became the most widely deployed version. Vixie cron added the @reboot, @daily, and similar macros, as well as the MAILTO variable for error reporting. This version (or derivatives) is what ships with most Linux distributions today — over 35 years after it was written.
The Quartz job scheduling library introduced a six-field cron format that added a Seconds field at the beginning and a Year field at the end. Quartz cron is the standard for Java applications and influenced the AWS EventBridge expression format.
AWS adapted the Quartz cron format for cloud infrastructure scheduling, with modifications for their specific use case. This brought cron syntax to cloud-scale infrastructure management, where expressions could trigger serverless functions, container tasks, and other cloud resources.
GitHub's CI/CD platform adopted standard 5-field cron for scheduled workflows, bringing cron into the modern DevOps workflow. Today millions of developers write GitHub Actions workflows with cron schedules to automate testing, deployment, and maintenance tasks.
Container orchestration and data pipeline platforms have made cron expressions part of the daily vocabulary for DevOps engineers and data engineers. Kubernetes CronJobs use standard cron to schedule batch workloads. Apache Airflow uses cron for DAG (Directed Acyclic Graph) scheduling. The expression format that Brian Kernighan wrote in 1975 now schedules tasks on some of the world's largest computing infrastructure.
Cron triggers jobs based on time. Message queues process tasks based on demand. For tasks that must run at specific times (daily reports, weekly backups), cron is the right tool. For tasks that should run in response to events (process every uploaded image, send email when user signs up), a message queue is the right tool. Many production systems use both: a cron job fires every hour to enqueue tasks that the queue workers process.
setInterval in JavaScript or time.sleep loops in Python run relative to when the process started. If your server restarts, the interval resets. Cron runs at absolute wall-clock times regardless of restarts. For production systems that need predictable, drift-free timing, cron is more reliable than application-level interval loops.
Cron executes a command at a scheduled time with no awareness of dependencies between jobs. Workflow orchestrators like Airflow define directed acyclic graphs where Job B only starts after Job A succeeds. For simple isolated tasks, cron is sufficient. For complex pipelines where task B depends on task A's output, use a workflow orchestrator — which itself often uses cron expressions for its schedule.
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