Field-by-Field Breakdown of `0 0 1 * *`
| Position | Field Name | Allowed Values | Value in `0 0 1 * *` | Evaluation Meaning |
|---|---|---|---|---|
| 1 | Minute | 0 – 59 | 0 | 0 (At minute 0) |
| 2 | Hour | 0 – 23 | 0 | 0 (At midnight / 00:00) |
| 3 | Day of Month | 1 – 31 | 1 | 1 (1st day of the month) |
| 4 | Month | 1 – 12 | * | * (Every month: Jan through Dec) |
| 5 | Day of Week | 0 – 6 (Sun-Sat) | * | * (Any day of the week) |
Monthly Billing & Accounting Cycle Mechanics
The first day of the month (`0 0 1 * *`) is the primary trigger for SaaS subscription renewals, monthly quota resets, invoice PDF generation, and accounting ledger closing.
The special string `@monthly` is an exact shortcut for `0 0 1 * *`. When the cron daemon reaches midnight on the transition from the last day of the prior month to the 1st, this task fires.
Because month lengths vary (28, 29, 30, or 31 days), scheduling on day `1` guarantees that the task runs every single month without exception, avoiding the notorious 'day 31 skip' bug.
Common Production Scenarios for `0 0 1 * *`
Monthly User API Quota & Rate Limit Reset
Resets monthly API request counters and credit balances in Redis for all active subscription tiers.
/usr/bin/python3 /opt/billing/reset_monthly_quotas.pyMonthly Accounting Summary & Tax Statement Export
Closes the prior month's accounting ledger and generates VAT/sales tax reports for external accountants.
/usr/bin/node /opt/finance/close_monthly_ledger.jsAutomated Monthly Customer Invoicing Batch
Generates monthly PDF invoices and initiates card payments via Stripe Invoicing API for enterprise accounts.
/usr/bin/php /var/www/artisan billing:generate-invoicesProduction Gotchas When Running `0 0 1 * *`
- The Day 31 Trap: Never schedule monthly tasks on day 31 (`0 0 31 * *`), as the job will be completely skipped in February, April, June, September, and November.
- High First-of-Month Workload: Scheduling all customer charge attempts at 00:00 on the 1st can overwhelm database queues and trigger bank fraud flags. Spread billing across hours.
- Timezone Considerations: If billing users globally, a single midnight UTC job may bill users in Australia 10 hours into the 1st, while California users are billed on the 31st.
Frequently Asked Questions About `0 0 1 * *`
Can I use `@monthly` instead of `0 0 1 * *`?
Yes, `@monthly` is an exact alias for `0 0 1 * *`.
What happens if I schedule a job on the 31st instead of the 1st?
It will only execute 7 times a year (January, March, May, July, August, October, December) and will be skipped in all 30-day and 28-day months.
How do I run a job on the last day of every month?
Standard POSIX cron does not support an 'L' (last day) flag natively. The standard practice is to run a script daily between days 28-31 and check if tomorrow's date is day 1: `[ $(date +\%d -d tomorrow) = 01 ] && /path/to/script.sh`.