Cron Syntax

A cron expression is how you tell node-cron when a task should run. node-cron uses the standard cron format with five or six fields, where the leading seconds field is optional.

# ┌────────────── second (optional)
# │ ┌──────────── minute
# │ │ ┌────────── hour
# │ │ │ ┌──────── day of month
# │ │ │ │ ┌────── month
# │ │ │ │ │ ┌──── day of week
# │ │ │ │ │ │
# * * * * * *

When you provide five fields, the seconds field defaults to 0 (the task runs at the start of the matched minute). Provide six fields to schedule down to the second.

Allowed values per field

Field	Values
second	0-59 (optional)
minute	0-59
hour	0-23
day of month	1-31 (or L for the last day)
month	1-12 (or names, e.g. Jan, Sep)
day of week	0-7 (or names; 0 and 7 are Sunday)

Each field also accepts * (any value), ranges, steps, and comma-separated lists, described below.

Common schedules

Copy-paste reference for the expressions you'll reach for most often:

Expression	Runs
* * * * *	Every minute
*/5 * * * *	Every 5 minutes
0 * * * *	Every hour, on the hour
0 0 * * *	Every day at midnight
0 3 * * *	Every day at 03:00
0 9 * * 1-5	At 09:00, Monday through Friday
0 0 1 * *	At midnight on the 1st of each month
0 0 L * *	At midnight on the last day of each month
0 0 * * 0	At midnight every Sunday
*/30 * * * * *	Every 30 seconds (6-field form)

Building expressions

Lists: multiple specific values

Use commas to run a task at several specific values in a field.

import cron from 'node-cron';

// Runs at minutes 1, 2, 4, and 5 of every hour
cron.schedule('1,2,4,5 * * * *', () => {
  console.log('Running at minutes 1, 2, 4, and 5 of each hour');
});

This expression has five fields, so the seconds field is omitted and defaults to 0.

Ranges: a continuous interval

Use a dash (-) to define an inclusive range.

import cron from 'node-cron';

// Runs every minute from minute 1 to minute 5 (inclusive) of every hour
cron.schedule('1-5 * * * *', () => {
  console.log('Running every minute from 1 to 5');
});

This is equivalent to 1,2,3,4,5, a cleaner way to express consecutive values.

Steps: periodic intervals

Use a slash (/) after a wildcard or range to define a step.

import cron from 'node-cron';

// Every 2 minutes (even minutes: 0, 2, 4, ...)
cron.schedule('*/2 * * * *', () => {
  console.log('Running every 2 minutes (even minutes)');
});

// Every 2 minutes starting from 1 (odd minutes: 1, 3, 5, ...)
cron.schedule('1-59/2 * * * *', () => {
  console.log('Running every 2 minutes starting from 1 (odd minutes)');
});

• */2 means "every 2 units" across the field's full range (0-59 for minutes), covering all even minutes.
• 1-59/2 means "every 2 units starting from 1", covering all odd minutes.

Names: months and weekdays

For readability, use full or abbreviated names instead of numbers for months and days of the week.

import cron from 'node-cron';

// Every minute on Sundays in January and September
cron.schedule('* * * January,September Sunday', () => {
  console.log('Running on Sundays in January and September');
});

// Same schedule using short names
cron.schedule('* * * Jan,Sep Sun', () => {
  console.log('Running on Sundays in Jan and Sep');
});

Last day of the month: L

In the day of month field, L (or lowercase l) means the last calendar day of the month. node-cron resolves it per month, so it lands on the 28th, 29th, 30th, or 31st as appropriate, including leap years.

import cron from 'node-cron';

// Runs at 12:00 on the last day of every month
cron.schedule('0 0 12 L * *', () => {
  console.log('Running on the last day of the month');
});

You can combine L with explicit days in a list:

import cron from 'node-cron';

// Runs at midnight on the 15th and on the last day of every month
cron.schedule('0 0 15,L * *', () => {
  console.log('Running on the 15th and the last day');
});

L is valid only in the day of month field. Using it in any other field, or variants such as LW, is rejected by validate.

Validating expressions

Not sure an expression is valid? Check it before scheduling:

import cron from 'node-cron';

cron.validate('0 12 * * *'); // true
cron.validate('not a cron'); // false

For tooling and richer error messages, two more helpers go beyond a boolean:

• validateDetailed(expr) returns every problem (which field, value, and why) without throwing.
• parse(expr) returns the decomposed fields, or throws on the first invalid one.

import { validateDetailed } from 'node-cron';

validateDetailed('99 12 * * 9').errors;
// [ { field: 'minute', value: '99', ... }, { field: 'dayOfWeek', value: '9', ... } ]

See validate, validateDetailed, and parse in the API reference.

Next steps

Now that you can describe when a task runs, learn how to manage it once it's running:

• Task Lifecycle & Status: start, stop, inspect, and destroy tasks.
• Scheduling Options: timezones, overlap prevention, and limits.