What does a cron expression look like?+
A standard cron expression has 5 fields: minute hour day-of-month month day-of-week. For example, '0 9 * * 1' means 'every Monday at 9:00 AM'. Some systems add a 6th field for seconds.
What does the asterisk (*) mean in cron?+
An asterisk means 'every' - so * in the hour field means 'every hour', and * in the minute field means 'every minute'. '*/5' in the minute field means 'every 5 minutes'.
How do I run a job every 15 minutes?+
Use the expression: */15 * * * *. This runs at minutes 0, 15, 30, and 45 of every hour, every day.
Is cron timezone-aware?+
Standard Unix cron runs in the server's local timezone. AWS EventBridge and some other systems support explicit timezone configuration. Always document what timezone your cron jobs run in.
What is the difference between 5-field, 6-field, and 7-field cron syntax?+
Standard Unix cron uses 5 fields (minute through weekday). Some systems like Spring Scheduler and Quartz add a seconds field at the start (making 6 fields). Some cloud schedulers add a year field at the end (making 7 fields). Check your scheduler's documentation to confirm the field order and whether it uses 0 or 1 for January.
How do I schedule a cron job to run every 15 minutes during business hours only?+
Use: */15 9-17 * * 1-5 - this runs every 15 minutes from 9am to 5pm, Monday to Friday. The 9-17 range in the hour field restricts to business hours and 1-5 in the weekday field restricts to Monday through Friday.
How does timezone handling work in cron and cloud schedulers?+
Standard crontab uses the server's local timezone defined in /etc/timezone. Set CRON_TZ=America/New_York at the top of the crontab to override per-user. AWS EventBridge, GitHub Actions, and Kubernetes CronJobs have their own timezone configuration fields - check their docs to avoid surprises around DST transitions.
How can I test a cron expression before deploying it to production?+
Paste your expression into this generator to see the next 10 run times listed in plain English. Double-check edge cases like month boundaries and DST transitions. For production verification, use your scheduler's built-in preview (AWS EventBridge shows next fire times) before enabling the job.