Cron Expression for the First Day of Each Month

Reading 0 0 1 * *

The five cron fields are minute, hour, day of month, month, day of week. In 0 0 1 * *:

• 0 — at minute zero.
• 0 — at midnight (hour zero).
• 1 — on day 1 of the month.
• First * — every month.
• Second * — every day of the week (ignored when day-of-month is set).

The day-of-month field accepts 1–31. Putting 1 there pins the job to the first calendar day of every month — January 1, February 1, March 1 and so on — always at 12:00 AM in the system's local timezone. Cron simply skips nonexistent days (there is no February 30), so an expression like 0 0 31 * * would fire only in months that have 31 days.

Where monthly jobs show up

The first of the month is the default boundary for billing and reporting: invoice generation, subscription renewals, statement runs, tax reconciliation and monthly KPI rollups all slot naturally into 0 0 1 * *. It is also the idiomatic schedule for customer lifecycle jobs — resetting monthly usage counters, expiring unused seats, and closing the books on the previous period.

The dom/dow OR quirk

A subtlety worth knowing: if you also set the day-of-week field, most cron daemons treat the two date fields with OR semantics — the job runs when either matches. In 0 0 1 * * the day-of-week field is *, so the job runs purely on the 1st. The moment you write something like 0 0 1 * 1, most daemons would fire on the 1st and on every Monday, which is rarely intended.

For other recurring boundaries, compare the daily reset 0 0 * * *, the weekly Monday schedule, and the range syntax used by weekdays-only. A full field-by-field reference, including month names like JAN–DEC, lives in the complete cron guide.