What does each field in a cron expression mean?+
Standard cron has 5 fields: minute (0-59), hour (0-23), day of month (1-31), month (1-12), day of week (0-7, where 0 and 7 are Sunday). Some systems add a 6th field for seconds at the start.
What does * mean in cron?+
* means every valid value. In the minute field, * means every minute. */5 means every 5 minutes. '0 * * * *' means at minute 0 of every hour (hourly).
How do I run a cron job every 15 minutes?+
Use: */15 * * * * - this runs at 0, 15, 30, and 45 minutes of every hour. To run only during business hours: */15 9-17 * * 1-5.
What time zone do cron jobs use?+
Most systems run cron in UTC by default. If you need a specific time zone, set CRON_TZ=America/New_York in your crontab, or calculate the UTC offset manually. Cloud schedulers (GitHub Actions, AWS EventBridge) let you specify time zones.