Cron Expression Parser

Tool guide

What is Cron Expression Parser?

Cron Expression Parser validates common five- or six-field schedules and calculates the next five occurrences from a chosen starting instant. UTC or the browser's local IANA timezone can be selected, and results are shown as ISO instants so cross-day, weekday, daylight-saving, and offset effects remain explicit. Common workflows include the following. Check whether a server job will run on the expected weekdays. Review a high-frequency schedule that includes a seconds field. Compare the next occurrences of one rule in UTC and local time. The page also documents input boundaries, output behavior, and practical cautions so you can review the result before putting it into an application, configuration, test, or production workflow.

When to use it

Check whether a server job will run on the expected weekdays.
Review a high-frequency schedule that includes a seconds field.
Compare the next occurrences of one rule in UTC and local time.

How to use it

Enter a five- or six-field Cron expression.
Choose the timezone and starting instant.
Parse and review the next ISO timestamps.
Load one of the realistic examples first to verify the selected options and processing direction before replacing it with your own data.
Review the output, status message, and documented limits; copy, download, or continue only after the result matches your expectation.

Runnable examples

The “Example 1” and “Example 2” buttons load the matching inputs. They cover different structures, directions, or boundaries and can be run directly in the workspace.

Example 1

0 9 * * 1-5

Example 2

*/15 8-18 * * 1-5

Input rules

Five-field expressions begin with minutes; six-field expressions begin with seconds.
The starting value must be a valid date-time understood by JavaScript.
The timezone must be supported by the browser and parser; vendor-specific extensions may differ.
Text input is counted before processing and is limited to 500 characters on this page; file modes apply the separate file limit shown in the workspace.
Cron implementations differ on extensions.

Output rules

Successful parsing lists the next five ISO instants in chronological order.
Results depend on timezone, daylight-saving rules, and the starting instant.
A valid result does not prove that another cloud platform or operating system uses identical Cron semantics.
Output reflects only the current input, direction, and options; rerun after changing a mode or value instead of treating an earlier result as current.
Results depend on the selected IANA timezone and DST rules.

Limitations and cautions

Cron implementations differ on extensions.
Results depend on the selected IANA timezone and DST rules.
The page does not connect to or save a server schedule.

How your data is handled

The expression, start time, and timezone are calculated locally. The page does not create a scheduled job, access a calendar, or retain the schedule.

FAQ

Is a seconds field supported?

Yes for six-field expressions; five fields start with minutes.

How are day-of-month and day-of-week combined?

The parser uses common non-strict Cron behavior; verify against the platform where the schedule will run.

Does this create a scheduled job?

No. It only parses and calculates times locally.

Are L, W, #, and other extensions supported?

Support depends on the parser version, and platforms differ. Verify any production expression against the destination platform's documentation and tests.

What happens during daylight-saving changes?

The selected IANA timezone rules apply, so skipped or repeated wall-clock times can affect the actual occurrence on that date.

Is the starting instant included?

The page calculates occurrences after the starting instant. Test the same boundary in the target scheduler when exact inclusion behavior matters.