Check when a schedule actually fires and compare the field and time-zone rules used by Unix, GitHub Actions, and AWS EventBridge.
Standard Unix five-field schedule. Review the next runs to confirm day-of-month and weekday behavior.
| Platform | Fields | Time zone |
|---|---|---|
| Unix | min hour day month weekday | System or configured zone |
| GitHub Actions | min hour day month weekday | UTC |
| AWS EventBridge | min hour day month weekday year | UTC |
A cron expression describes a recurring schedule using compact fields for minute, hour, day, month, and weekday. Traditional Unix crontab uses five fields. Other platforms borrow the syntax but change the number of fields, supported extensions, and evaluation time zone.
This debugger parses common lists, ranges, wildcards, names, and step values, then searches forward for matching times. Always compare its results with the documentation and preview provided by the platform that will execute the job.
minute hour day-of-month month day-of-week
The expression 0 9 * * 1-5 runs at 09:00 from Monday through Friday. In many Unix cron implementations, day-of-month and day-of-week use OR behavior when both are restricted: a match in either field can trigger the command. That rule surprises people expecting both fields to match.
GitHub Actions uses the five-field POSIX-style syntax in scheduled workflows and evaluates it in UTC. A repository workflow scheduled for 0 9 * * * therefore runs around 09:00 UTC, not necessarily 09:00 in the repository owner's local time.
Scheduled automation is not a real-time timer. Providers can delay work during heavy load, disable schedules in inactive repositories, or apply minimum-frequency limits. Do not use cron alone for safety-critical deadlines.
EventBridge scheduled rules use six fields:
minute hour day-of-month month day-of-week year
One of the two day fields must normally contain ?, meaning “no specific value.” For example, cron(0 9 ? * MON-FRI *) represents weekdays at 09:00 UTC. This debugger supports ordinary wildcards, ranges, lists, steps, and month or weekday names. It does not currently evaluate the L, W, or # extensions.
The same local clock time can correspond to different UTC offsets through the year. A schedule evaluated in Europe/Oslo may skip or repeat a local time around a daylight-saving transition. GitHub Actions and EventBridge results are shown in UTC to match their basic scheduled-rule behavior.
Check several future runs, including month boundaries, weekends, and daylight-saving changes. Confirm whether the destination accepts Sunday as 0, 7, or a name, and whether it supports nonstandard seconds or year fields.
Cron expressions entered here stay in your browser. Use the World Clock to compare time zones, the ICS File Generator for shareable calendar events, or the Business Days Calculator for working-day intervals.
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