Cron Expression Cheatsheet

Anatomy of a Cron Expression

A standard cron expression is a string of five fields separated by spaces. Each field represents a different unit of time and controls when a scheduled task fires. Reading from left to right, the fields are: minute, hour, day of month, month, and day of week.

┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12 or JAN-DEC)
│ │ │ │ ┌───────────── day of week (0-7 or SUN-SAT)
│ │ │ │ │
* * * * *

Field-by-Field Breakdown

Each field accepts specific values and special characters. Understanding the allowed ranges is essential for writing correct expressions.

Special Characters Explained

Cron expressions support several special characters that give you fine-grained control over scheduling. Here is what each one does and when to use it.

Asterisk (*) - Every Value

The asterisk matches every possible value for a field. For example, * in the hour field means “every hour” and * in the day-of-week field means “every day of the week.”

# Every minute of every hour of every day
* * * * *

# Every hour at minute 0
0 * * * *

Comma (,) - List of Values

Commas let you specify a list of discrete values. This is useful when your schedule doesn't follow a regular interval and you need to fire at specific times.

# At 8:00 AM, 12:00 PM, and 6:00 PM
0 8,12,18 * * *

# On Monday, Wednesday, and Friday
0 9 * * 1,3,5

Hyphen (-) - Range of Values

Hyphens define an inclusive range. All values from the start to the end are included. This is commonly used for business hours or weekday schedules.

# Every minute during business hours (9 AM to 5 PM)
* 9-17 * * *

# Weekdays only (Monday through Friday)
0 9 * * 1-5

Slash (/) - Step Values

The slash specifies intervals. The value before the slash is the starting point, and the value after is the step. */5 in the minute field means “every 5 minutes” and is equivalent to 0,5,10,15,20,25,30,35,40,45,50,55.

# Every 5 minutes
*/5 * * * *

# Every 2 hours starting at midnight
0 */2 * * *

# Every 10 minutes between minutes 5 and 55
5/10 * * * *    # fires at 5, 15, 25, 35, 45, 55

L - Last

The L character is supported in some cron implementations (Quartz, Spring, AWS) and means “last.” In the day-of-month field, L means the last day of the month. In the day-of-week field, 5L means the last Friday.

# Last day of every month at midnight
0 0 L * *

# Last Friday of every month at 5 PM
0 17 * * 5L

W - Nearest Weekday

The W character finds the nearest weekday (Monday-Friday) to the given day. For example, 15W means “the nearest weekday to the 15th.” If the 15th is a Saturday, it fires on Friday the 14th. If the 15th is a Sunday, it fires on Monday the 16th.

# Nearest weekday to the 1st of each month
0 9 1W * *

# Last weekday of every month
0 9 LW * *

Hash (#) - Nth Day of Week

The # character specifies the Nth occurrence of a day in a month. For example, 2#1 means “the first Monday of the month” (where 2 = Monday in some systems). This is particularly useful for scheduling monthly meetings.

# First Monday of every month at 10 AM
0 10 * * 1#1

# Third Wednesday of every month
0 14 * * 3#3

Quick Reference: Common Expressions

Here are the most frequently used cron expressions that every developer should know.

Standard vs Extended (6-Field) Format

The standard Unix cron format uses 5 fields. However, some systems (Quartz Scheduler, Spring Framework, AWS CloudWatch) support an extended 6-field format that adds a seconds field at the beginning.

┌───────────── second (0-59)       ← additional field
│ ┌───────────── minute (0-59)
│ │ ┌───────────── hour (0-23)
│ │ │ ┌───────────── day of month (1-31)
│ │ │ │ ┌───────────── month (1-12)
│ │ │ │ │ ┌───────────── day of week (0-7)
│ │ │ │ │ │
0 * * * * *

When you encounter a cron expression with 6 fields, the leftmost field is seconds. This format is common in Java-based systems.

Platform Differences

Different platforms have subtle differences in their cron implementations. These differences can trip you up when migrating schedules between systems.

• Day of week numbering: In standard Unix cron, 0 = Sunday, 7 = Sunday. In Quartz Scheduler, 1 = Sunday, 7 = Saturday.
• Question mark (?): Some systems (Quartz, AWS EventBridge) support ? in the day-of-month or day-of-week fields to mean “no specific value.” Standard cron does not support this.
• Year field: AWS EventBridge supports a 7th field for year. Standard cron and most other systems do not.
• L, W, # characters: These are not supported in standard Unix cron. They were introduced by Quartz Scheduler and adopted by some cloud platforms.

Common Mistakes

Even experienced developers make these cron expression errors. Being aware of them can save hours of debugging.

• Confusing field order: Many developers accidentally swap the minute and hour fields. 9 0 * * * fires at 12:09 AM, not 9:00 AM. The correct expression for 9:00 AM is 0 9 * * *.
• Using both day fields: When specifying both day-of-month and day-of-week, the behavior varies by platform. In standard Unix cron, the job runs when either condition is met (OR logic). In Quartz, you must use ? in one of the two fields.
• Forgetting server timezone: Cron runs in the server's timezone unless explicitly configured otherwise. A schedule set for 9 AM will fire at 9 AM server time, which may differ from your local time.
• Step values start point: */5 means “every 5 starting from 0” (0, 5, 10, ...), not “every 5 starting from now.” If you need to start at a specific offset, use 2/5 (2, 7, 12, ...).

Build and Test Your Expressions

Rather than writing cron expressions by hand and hoping they are correct, use our interactive Cron Expression Builder to visually construct expressions, see their next execution times, and verify they match your intended schedule.