Cron Every Night at 3 AM

The cron expression 0 3 * * * schedules a task to run once per day at exactly 3:00 AM.

Field-by-field breakdown:

• 0 (Minute): At minute 0. The task fires at the top of the hour.
• 3 (Hour): At hour 3 (3 AM). The task is restricted to the 3 AM hour, deep in the off-peak overnight window.
• * (Day of Month): Every day from 1 through 31. No restriction on the day of the month.
• * (Month): Every month from January through December. No restriction on which month.
• * (Day of Week): Every day of the week from Sunday through Saturday. No restriction on the day of the week.

This means your task will execute once per day at 3:00 AM server time. The 3 AM slot is excellent for heavy batch processing because it avoids the 2 AM daylight saving time transition issues that affect many time zones (since clocks jump from 2 AM to 3 AM, 3 AM always exists during spring forward). It also provides sufficient distance from both midnight cleanup jobs and early-morning pre-business-hours preparation tasks. If your nightly job takes a long time to run, scheduling at 3 AM gives it several hours to complete before business hours begin. This expression is supported by standard cron on Linux/macOS, as well as cloud services like AWS CloudWatch, Google Cloud Scheduler, and GitHub Actions.