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Cron Expression Explainer

Explain five-field cron expressions or export GitHub Actions and Kubernetes schedule fragments with a named timezone.

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Exports accept numeric five-field cron. GitHub export requires five-minute spacing across a repeated day, including midnight.

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Explain five-field cron expressions or export GitHub Actions and Kubernetes schedule fragments with a named timezone.

This tool runs open-source code from OmniTools (MIT License). See open-source credits.

Cron Expression Explainer: A cron expression describes a recurring schedule using minute, hour, day of month, month, and day of week fields. Explain expressions in plain language, or create a schedule fragment for GitHub Actions or Kubernetes with a named timezone.

Description mode returns one explanation per line. Export mode returns a YAML schedule fragment with explicit timezone settings.

  • Explain an unfamiliar five-field cron expression before changing a scheduled job.
  • Create GitHub Actions schedule entries with an explicit timezone instead of manually converting to UTC.
  • Set a Kubernetes CronJob schedule and spec.timeZone together.

Sources: GitHub Actions: schedule syntax and timezones; Kubernetes CronJob: time zones

Instructions

  1. Enter one five-field expression per line, without a command. For example, 30 9 * * 1-5 means 09:30 on weekdays.
  2. Keep Plain-language descriptions to explain the input. Choose a schedule YAML format to export platform settings.
  3. For export, enter a named IANA timezone such as America/New_York. Kubernetes accepts one expression per export.
  4. Review the output, then copy the fragment into the matching on or spec block in your existing configuration.

Example

Input: 30 9 * * 1-5

Settings: Output format Plain-language descriptions

Result: At 09:30 AM, Monday through Friday

Day-of-week values run from 0 for Sunday. The range 1-5 therefore means Monday through Friday.

Limits

  • The tool creates configuration text. It does not register, run, or monitor a job.
  • Export accepts numeric fields, *, ranges, lists, and steps. Use 0 through 6 for Sunday through Saturday.
  • Export rejects names, seconds, commands, timezone prefixes, and Quartz-specific ?, L, W, or # syntax.
  • GitHub export requires five-minute spacing across a repeated day, including midnight. This conservative rule can reject schedules on separated dates.
  • A fragment is not a complete workflow or CronJob. Merge its settings into an existing configuration with jobs or jobTemplate.
  • Kubernetes timeZone is stable from version 1.27. Put the timezone in spec.timeZone, not inside the cron expression.
  • Descriptions do not predict execution dates or daylight-saving transitions. Check the target scheduler's timezone rules and current documentation.
  • Syntax checks do not prove that a calendar date exists or that the scheduler will run a job on time.

Questions

How do I explain a cron expression in plain language?

Paste one five-field expression per line without a command. Keep Plain-language descriptions to read the schedule for each line.

Can I use a local timezone in GitHub Actions schedules?

Yes. GitHub Actions supports a timezone field beside each cron entry. Choose GitHub Actions schedule YAML and enter a named IANA timezone. Merge the output into the on block of an existing workflow.

Where does a Kubernetes CronJob timezone belong?

Set spec.timeZone beside spec.schedule. The field is stable from Kubernetes 1.27. Do not put TZ or CRON_TZ inside the expression. Export one schedule at a time and merge it into an existing CronJob.

Which cron syntax can I export?

Export supports numeric five-field cron with *, ranges, lists, and steps. Use weekday numbers 0 through 6. Export rejects names, seconds, commands, timezone prefixes, and Quartz-specific syntax.

Why can GitHub export reject a valid calendar schedule?

This export requires five-minute spacing across a repeated day, including midnight. That conservative rule can reject schedules on separated dates. Description mode remains available to explain those expressions.

Can I remove the seconds field from any six-field expression?

No. Removing seconds can change the schedule. Check the source scheduler and intended times before translating a six-field or Quartz expression.

Does the tool run jobs or predict daylight-saving behavior?

No. It creates descriptions or configuration fragments. It does not register jobs or calculate execution dates. Check the target scheduler for daylight-saving behavior, delays, and other execution limits.