Cron expression for the first of every month

The cron expression 0 0 1 * * runs a job at midnight on the 1st of every month — 12 firings per year. The third field (1) constrains day-of-month to the first; the second 0 is the hour, the leading 0 is the minute. AWS EventBridge needs cron(0 0 1 * ? *) because its day-of-month and day-of-week can’t both be *.

Quick reference

What if I want the LAST day of the month?

Months have variable length (28, 29, 30 or 31 days), so “last day” is harder than “first”. Three approaches:

Unix cron (no native support):

0 0 28-31 * * /path/to/check-and-run.sh

The script runs every day from the 28th onward and exits early unless tomorrow is the 1st of next month — making the actual job execute only on the true last day:

#!/bin/bash
if [ "$(date -d tomorrow +%d)" = "01" ]; then
  exec /usr/local/bin/end-of-month-job
fi

AWS EventBridge: the L extension is supported natively.

cron(0 0 L * ? *)

This runs at midnight on the actual last day of each month — 28, 29, 30, or 31 depending on the month and year.

Quartz: also supports L.

0 0 0 L * ?

Variations

How do I use it on each platform?

Linux crontab:

0 0 1 * * /usr/local/bin/monthly-report

Or with the shortcut:

@monthly /usr/local/bin/monthly-report

Kubernetes CronJob:

apiVersion: batch/v1
kind: CronJob
metadata:
  name: monthly-report
spec:
  schedule: "0 0 1 * *"
  timeZone: "UTC"
  jobTemplate:
    spec:
      activeDeadlineSeconds: 3600    # monthly jobs often run long; cap them
      template:
        spec:
          containers:
            - name: report
              image: my-org/monthly-report:1.0
          restartPolicy: OnFailure

AWS EventBridge:

aws events put-rule \
  --name monthly-report \
  --schedule-expression "cron(0 0 1 * ? *)"

GitHub Actions:

on:
  schedule:
    - cron: '0 0 1 * *'

Common mistakes

Trying to use day-of-month 31. 0 0 31 * * only fires in months with 31 days — January, March, May, July, August, October, December. February, April, June, September and November are silently skipped. Use L (in AWS/Quartz) or a 28-31 + script pattern (in Unix) instead.

Combining * * 1 * 1 (1st of month AND every Monday). In Unix cron, day-of-month and day-of-week combine as OR, not AND. So this fires every Monday OR on the 1st — not “the 1st only if it’s a Monday”. To get the latter, use a script that filters.

Assuming @monthly works in AWS. AWS EventBridge does not accept @-style shortcuts. Use the explicit form cron(0 0 1 * ? *).

For other schedules see common cron schedules, or build a custom expression with the Cron Expression Builder.