Cron Every Day at 4 AM

The cron expression 0 4 * * * schedules a task to run once per day at exactly 4:00 AM.

Field-by-field breakdown:

• 0 (Minute): At minute 0. The task fires at the top of the hour.
• 4 (Hour): At hour 4 (4 AM). The task runs during the pre-dawn hours, typically the lowest usage period for most applications.
• * (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 4:00 AM server time. The 4 AM time slot is strategic for tasks that should complete before business hours begin. It avoids the congestion at midnight and the DST complications at 2 AM, while still providing a full 4-5 hours before a typical 8-9 AM business start. This makes it suitable for resource-intensive jobs like full database reindexing, large data exports, or comprehensive system scans that may take several hours to complete. Ensure your server's timezone is configured correctly, or use UTC-based scheduling for consistency. This expression is supported by standard cron on Linux/macOS, as well as cloud services like AWS CloudWatch, Google Cloud Scheduler, and GitHub Actions.