Cron 表示式產生器

A cron expression is a compact string of five fields that tells a scheduler when to run a task: minute, hour, day of month, month and day of week. It is powerful but easy to get wrong, and a misplaced asterisk can mean a job fires every minute instead of once a day.

Start from a common preset (every hour, every day at midnight, every Monday at 9 AM) or build a custom expression field by field, with each field labeled and validated as you type.

Crucially, it previews the next five run times in your browser's local time zone, so you can confirm the schedule actually does what you intended before you deploy it.

Each field accepts more than a single value: an asterisk means every value, a list like MON,WED,FRI picks several, a range like MON-FRI spans days, and a step like */15 in the minute field runs at 0, 15, 30 and 45 past the hour.

The output works with standard cron on Linux and macOS, crontab, AWS EventBridge, GitHub Actions schedules and most job-scheduling libraries.

One classic trap is setting both day-of-month and day-of-week: standard cron then runs when either matches, not both, so a job can fire more often than expected. Leaving one of the two as an asterisk avoids the surprise.

This tool targets standard five-field cron, so platform extensions like a seconds field or @reboot are not produced here. Remember too that the job runs in the executing server's time zone, which may differ from the local preview.